Add qemu 2.4.0
[kvmfornfv.git] / qemu / roms / ipxe / src / core / settings.c
diff --git a/qemu/roms/ipxe/src/core/settings.c b/qemu/roms/ipxe/src/core/settings.c
new file mode 100644 (file)
index 0000000..5e16b27
--- /dev/null
@@ -0,0 +1,2556 @@
+/*
+ * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+#include <byteswap.h>
+#include <errno.h>
+#include <assert.h>
+#include <ipxe/in.h>
+#include <ipxe/ip.h>
+#include <ipxe/ipv6.h>
+#include <ipxe/vsprintf.h>
+#include <ipxe/dhcp.h>
+#include <ipxe/uuid.h>
+#include <ipxe/uri.h>
+#include <ipxe/base16.h>
+#include <ipxe/pci.h>
+#include <ipxe/init.h>
+#include <ipxe/version.h>
+#include <ipxe/settings.h>
+
+/** @file
+ *
+ * Configuration settings
+ *
+ */
+
+/******************************************************************************
+ *
+ * Generic settings blocks
+ *
+ ******************************************************************************
+ */
+
+/**
+ * A generic setting
+ *
+ */
+struct generic_setting {
+       /** List of generic settings */
+       struct list_head list;
+       /** Setting */
+       struct setting setting;
+       /** Size of setting name */
+       size_t name_len;
+       /** Size of setting data */
+       size_t data_len;
+};
+
+/**
+ * Get generic setting name
+ *
+ * @v generic          Generic setting
+ * @ret name           Generic setting name
+ */
+static inline void * generic_setting_name ( struct generic_setting *generic ) {
+       return ( ( ( void * ) generic ) + sizeof ( *generic ) );
+}
+
+/**
+ * Get generic setting data
+ *
+ * @v generic          Generic setting
+ * @ret data           Generic setting data
+ */
+static inline void * generic_setting_data ( struct generic_setting *generic ) {
+       return ( ( ( void * ) generic ) + sizeof ( *generic ) +
+                generic->name_len );
+}
+
+/**
+ * Find generic setting
+ *
+ * @v generics         Generic settings block
+ * @v setting          Setting to find
+ * @ret generic                Generic setting, or NULL
+ */
+static struct generic_setting *
+find_generic_setting ( struct generic_settings *generics,
+                      const struct setting *setting ) {
+       struct generic_setting *generic;
+
+       list_for_each_entry ( generic, &generics->list, list ) {
+               if ( setting_cmp ( &generic->setting, setting ) == 0 )
+                       return generic;
+       }
+       return NULL;
+}
+
+/**
+ * Store value of generic setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting to store
+ * @v data             Setting data, or NULL to clear setting
+ * @v len              Length of setting data
+ * @ret rc             Return status code
+ */
+int generic_settings_store ( struct settings *settings,
+                            const struct setting *setting,
+                            const void *data, size_t len ) {
+       struct generic_settings *generics =
+               container_of ( settings, struct generic_settings, settings );
+       struct generic_setting *old;
+       struct generic_setting *new = NULL;
+       size_t name_len;
+
+       /* Identify existing generic setting, if any */
+       old = find_generic_setting ( generics, setting );
+
+       /* Create new generic setting, if required */
+       if ( len ) {
+               /* Allocate new generic setting */
+               name_len = ( strlen ( setting->name ) + 1 );
+               new = zalloc ( sizeof ( *new ) + name_len + len );
+               if ( ! new )
+                       return -ENOMEM;
+
+               /* Populate new generic setting */
+               new->name_len = name_len;
+               new->data_len = len;
+               memcpy ( &new->setting, setting, sizeof ( new->setting ) );
+               new->setting.name = generic_setting_name ( new );
+               memcpy ( generic_setting_name ( new ),
+                        setting->name, name_len );
+               memcpy ( generic_setting_data ( new ), data, len );
+       }
+
+       /* Delete existing generic setting, if any */
+       if ( old ) {
+               list_del ( &old->list );
+               free ( old );
+       }
+
+       /* Add new setting to list, if any */
+       if ( new )
+               list_add ( &new->list, &generics->list );
+
+       return 0;
+}
+
+/**
+ * Fetch value of generic setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting to fetch
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ */
+int generic_settings_fetch ( struct settings *settings,
+                            struct setting *setting,
+                            void *data, size_t len ) {
+       struct generic_settings *generics =
+               container_of ( settings, struct generic_settings, settings );
+       struct generic_setting *generic;
+
+       /* Find generic setting */
+       generic = find_generic_setting ( generics, setting );
+       if ( ! generic )
+               return -ENOENT;
+
+       /* Copy out generic setting data */
+       if ( len > generic->data_len )
+               len = generic->data_len;
+       memcpy ( data, generic_setting_data ( generic ), len );
+
+       /* Set setting type, if not yet specified */
+       if ( ! setting->type )
+               setting->type = generic->setting.type;
+
+       return generic->data_len;
+}
+
+/**
+ * Clear generic settings block
+ *
+ * @v settings         Settings block
+ */
+void generic_settings_clear ( struct settings *settings ) {
+       struct generic_settings *generics =
+               container_of ( settings, struct generic_settings, settings );
+       struct generic_setting *generic;
+       struct generic_setting *tmp;
+
+       list_for_each_entry_safe ( generic, tmp, &generics->list, list ) {
+               list_del ( &generic->list );
+               free ( generic );
+       }
+       assert ( list_empty ( &generics->list ) );
+}
+
+/** Generic settings operations */
+struct settings_operations generic_settings_operations = {
+       .store = generic_settings_store,
+       .fetch = generic_settings_fetch,
+       .clear = generic_settings_clear,
+};
+
+/******************************************************************************
+ *
+ * Registered settings blocks
+ *
+ ******************************************************************************
+ */
+
+/** Root generic settings block */
+struct generic_settings generic_settings_root = {
+       .settings = {
+               .refcnt = NULL,
+               .name = "",
+               .siblings =
+                   LIST_HEAD_INIT ( generic_settings_root.settings.siblings ),
+               .children =
+                   LIST_HEAD_INIT ( generic_settings_root.settings.children ),
+               .op = &generic_settings_operations,
+       },
+       .list = LIST_HEAD_INIT ( generic_settings_root.list ),
+};
+
+/** Root settings block */
+#define settings_root generic_settings_root.settings
+
+/** Autovivified settings block */
+struct autovivified_settings {
+       /** Reference count */
+       struct refcnt refcnt;
+       /** Generic settings block */
+       struct generic_settings generic;
+};
+
+/**
+ * Free autovivified settings block
+ *
+ * @v refcnt           Reference count
+ */
+static void autovivified_settings_free ( struct refcnt *refcnt ) {
+       struct autovivified_settings *autovivified =
+               container_of ( refcnt, struct autovivified_settings, refcnt );
+
+       generic_settings_clear ( &autovivified->generic.settings );
+       free ( autovivified );
+}
+
+/**
+ * Find child settings block
+ *
+ * @v parent           Parent settings block
+ * @v name             Name within this parent
+ * @ret settings       Settings block, or NULL
+ */
+struct settings * find_child_settings ( struct settings *parent,
+                                       const char *name ) {
+       struct settings *settings;
+
+       /* Find target parent settings block */
+       parent = settings_target ( parent );
+
+       /* Treat empty name as meaning "this block" */
+       if ( ! *name )
+               return parent;
+
+       /* Look for child with matching name */
+       list_for_each_entry ( settings, &parent->children, siblings ) {
+               if ( strcmp ( settings->name, name ) == 0 )
+                       return settings_target ( settings );
+       }
+
+       return NULL;
+}
+
+/**
+ * Find or create child settings block
+ *
+ * @v parent           Parent settings block
+ * @v name             Name within this parent
+ * @ret settings       Settings block, or NULL
+ */
+struct settings * autovivify_child_settings ( struct settings *parent,
+                                             const char *name ) {
+       struct {
+               struct autovivified_settings autovivified;
+               char name[ strlen ( name ) + 1 /* NUL */ ];
+       } *new_child;
+       struct settings *settings;
+
+       /* Find target parent settings block */
+       parent = settings_target ( parent );
+
+       /* Return existing settings, if existent */
+       if ( ( settings = find_child_settings ( parent, name ) ) != NULL )
+               return settings;
+
+       /* Create new generic settings block */
+       new_child = zalloc ( sizeof ( *new_child ) );
+       if ( ! new_child ) {
+               DBGC ( parent, "Settings %p could not create child %s\n",
+                      parent, name );
+               return NULL;
+       }
+       memcpy ( new_child->name, name, sizeof ( new_child->name ) );
+       ref_init ( &new_child->autovivified.refcnt,
+                  autovivified_settings_free );
+       generic_settings_init ( &new_child->autovivified.generic,
+                               &new_child->autovivified.refcnt );
+       settings = &new_child->autovivified.generic.settings;
+       register_settings ( settings, parent, new_child->name );
+       return settings;
+}
+
+/**
+ * Return settings block name
+ *
+ * @v settings         Settings block
+ * @ret name           Settings block name
+ */
+const char * settings_name ( struct settings *settings ) {
+       static char buf[16];
+       char tmp[ sizeof ( buf ) ];
+
+       /* Find target settings block */
+       settings = settings_target ( settings );
+
+       /* Construct name */
+       for ( buf[2] = buf[0] = 0 ; settings ; settings = settings->parent ) {
+               memcpy ( tmp, buf, sizeof ( tmp ) );
+               snprintf ( buf, sizeof ( buf ), ".%s%s", settings->name, tmp );
+       }
+       return ( buf + 2 );
+}
+
+/**
+ * Parse settings block name
+ *
+ * @v name             Name
+ * @v get_child                Function to find or create child settings block
+ * @ret settings       Settings block, or NULL
+ */
+static struct settings *
+parse_settings_name ( const char *name, get_child_settings_t get_child ) {
+       struct settings *settings = &settings_root;
+       char name_copy[ strlen ( name ) + 1 ];
+       char *subname;
+       char *remainder;
+
+       /* Create modifiable copy of name */
+       memcpy ( name_copy, name, sizeof ( name_copy ) );
+       remainder = name_copy;
+
+       /* Parse each name component in turn */
+       while ( remainder ) {
+               subname = remainder;
+               remainder = strchr ( subname, '.' );
+               if ( remainder )
+                       *(remainder++) = '\0';
+               settings = get_child ( settings, subname );
+               if ( ! settings )
+                       break;
+       }
+
+       return settings;
+}
+
+/**
+ * Find settings block
+ *
+ * @v name             Name
+ * @ret settings       Settings block, or NULL
+ */
+struct settings * find_settings ( const char *name ) {
+
+       return parse_settings_name ( name, find_child_settings );
+}
+
+/**
+ * Apply all settings
+ *
+ * @ret rc             Return status code
+ */
+static int apply_settings ( void ) {
+       struct settings_applicator *applicator;
+       int rc;
+
+       /* Call all settings applicators */
+       for_each_table_entry ( applicator, SETTINGS_APPLICATORS ) {
+               if ( ( rc = applicator->apply() ) != 0 ) {
+                       DBG ( "Could not apply settings using applicator "
+                             "%p: %s\n", applicator, strerror ( rc ) );
+                       return rc;
+               }
+       }
+
+       return 0;
+}
+
+/**
+ * Reprioritise settings
+ *
+ * @v settings         Settings block
+ *
+ * Reorders the settings block amongst its siblings according to its
+ * priority.
+ */
+static void reprioritise_settings ( struct settings *settings ) {
+       struct settings *parent = settings->parent;
+       long priority;
+       struct settings *tmp;
+       long tmp_priority;
+
+       /* Stop when we reach the top of the tree */
+       if ( ! parent )
+               return;
+
+       /* Read priority, if present */
+       priority = fetch_intz_setting ( settings, &priority_setting );
+
+       /* Remove from siblings list */
+       list_del ( &settings->siblings );
+
+       /* Reinsert after any existing blocks which have a higher priority */
+       list_for_each_entry ( tmp, &parent->children, siblings ) {
+               tmp_priority = fetch_intz_setting ( tmp, &priority_setting );
+               if ( priority > tmp_priority )
+                       break;
+       }
+       list_add_tail ( &settings->siblings, &tmp->siblings );
+
+       /* Recurse up the tree */
+       reprioritise_settings ( parent );
+}
+
+/**
+ * Register settings block
+ *
+ * @v settings         Settings block
+ * @v parent           Parent settings block, or NULL
+ * @v name             Settings block name
+ * @ret rc             Return status code
+ */
+int register_settings ( struct settings *settings, struct settings *parent,
+                       const char *name ) {
+       struct settings *old_settings;
+
+       /* Sanity check */
+       assert ( settings != NULL );
+
+       /* Find target parent settings block */
+       parent = settings_target ( parent );
+
+       /* Apply settings block name */
+       settings->name = name;
+
+       /* Remove any existing settings with the same name */
+       if ( ( old_settings = find_child_settings ( parent, settings->name ) ))
+               unregister_settings ( old_settings );
+
+       /* Add to list of settings */
+       ref_get ( settings->refcnt );
+       ref_get ( parent->refcnt );
+       settings->parent = parent;
+       list_add_tail ( &settings->siblings, &parent->children );
+       DBGC ( settings, "Settings %p (\"%s\") registered\n",
+              settings, settings_name ( settings ) );
+
+       /* Fix up settings priority */
+       reprioritise_settings ( settings );
+
+       /* Apply potentially-updated settings */
+       apply_settings();
+
+       return 0;
+}
+
+/**
+ * Unregister settings block
+ *
+ * @v settings         Settings block
+ */
+void unregister_settings ( struct settings *settings ) {
+       struct settings *child;
+       struct settings *tmp;
+
+       /* Unregister child settings */
+       list_for_each_entry_safe ( child, tmp, &settings->children, siblings ) {
+               unregister_settings ( child );
+       }
+
+       DBGC ( settings, "Settings %p (\"%s\") unregistered\n",
+              settings, settings_name ( settings ) );
+
+       /* Remove from list of settings */
+       ref_put ( settings->parent->refcnt );
+       settings->parent = NULL;
+       list_del ( &settings->siblings );
+       ref_put ( settings->refcnt );
+
+       /* Apply potentially-updated settings */
+       apply_settings();
+}
+
+/******************************************************************************
+ *
+ * Core settings routines
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Redirect to target settings block
+ *
+ * @v settings         Settings block, or NULL
+ * @ret settings       Underlying settings block
+ */
+struct settings * settings_target ( struct settings *settings ) {
+
+       /* NULL settings implies the global settings root */
+       if ( ! settings )
+               settings = &settings_root;
+
+       /* Redirect to underlying settings block, if applicable */
+       if ( settings->op->redirect )
+               return settings->op->redirect ( settings );
+
+       /* Otherwise, return this settings block */
+       return settings;
+}
+
+/**
+ * Check applicability of setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting
+ * @ret applies                Setting applies within this settings block
+ */
+int setting_applies ( struct settings *settings,
+                     const struct setting *setting ) {
+
+       /* Find target settings block */
+       settings = settings_target ( settings );
+
+       /* Check applicability of setting */
+       return ( settings->op->applies ?
+                settings->op->applies ( settings, setting ) : 1 );
+}
+
+/**
+ * Find setting applicable to settings block, if any
+ *
+ * @v settings         Settings block
+ * @v setting          Setting
+ * @ret setting                Applicable setting, if any
+ */
+static const struct setting *
+applicable_setting ( struct settings *settings, const struct setting *setting ){
+       const struct setting *applicable;
+
+       /* If setting is already applicable, use it */
+       if ( setting_applies ( settings, setting ) )
+               return setting;
+
+       /* Otherwise, look for a matching predefined setting which does apply */
+       for_each_table_entry ( applicable, SETTINGS ) {
+               if ( ( setting_cmp ( setting, applicable ) == 0 ) &&
+                    ( setting_applies ( settings, applicable ) ) )
+                       return applicable;
+       }
+
+       return NULL;
+}
+
+/**
+ * Store value of setting
+ *
+ * @v settings         Settings block, or NULL
+ * @v setting          Setting to store
+ * @v data             Setting data, or NULL to clear setting
+ * @v len              Length of setting data
+ * @ret rc             Return status code
+ */
+int store_setting ( struct settings *settings, const struct setting *setting,
+                   const void *data, size_t len ) {
+       int rc;
+
+       /* Find target settings block */
+       settings = settings_target ( settings );
+
+       /* Fail if setting does not apply to this settings block */
+       if ( ! setting_applies ( settings, setting ) )
+               return -ENOTTY;
+
+       /* Sanity check */
+       if ( ! settings->op->store )
+               return -ENOTSUP;
+
+       /* Store setting */
+       if ( ( rc = settings->op->store ( settings, setting,
+                                         data, len ) ) != 0 )
+               return rc;
+
+       /* Reprioritise settings if necessary */
+       if ( setting_cmp ( setting, &priority_setting ) == 0 )
+               reprioritise_settings ( settings );
+
+       /* If these settings are registered, apply potentially-updated
+        * settings
+        */
+       for ( ; settings ; settings = settings->parent ) {
+               if ( settings == &settings_root ) {
+                       if ( ( rc = apply_settings() ) != 0 )
+                               return rc;
+                       break;
+               }
+       }
+
+       return 0;
+}
+
+/**
+ * Fetch setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v origin           Origin of setting to fill in, or NULL
+ * @v fetched          Fetched setting to fill in, or NULL
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ *
+ * The actual length of the setting will be returned even if
+ * the buffer was too small.
+ */
+int fetch_setting ( struct settings *settings, const struct setting *setting,
+                   struct settings **origin, struct setting *fetched,
+                   void *data, size_t len ) {
+       const struct setting *applicable;
+       struct settings *child;
+       struct setting tmp;
+       int ret;
+
+       /* Avoid returning uninitialised data on error */
+       memset ( data, 0, len );
+       if ( origin )
+               *origin = NULL;
+       if ( fetched )
+               memcpy ( fetched, setting, sizeof ( *fetched ) );
+
+       /* Find target settings block */
+       settings = settings_target ( settings );
+
+       /* Sanity check */
+       if ( ! settings->op->fetch )
+               return -ENOTSUP;
+
+       /* Try this block first, if an applicable setting exists */
+       if ( ( applicable = applicable_setting ( settings, setting ) ) ) {
+
+               /* Create modifiable copy of setting */
+               memcpy ( &tmp, applicable, sizeof ( tmp ) );
+               if ( ( ret = settings->op->fetch ( settings, &tmp,
+                                                  data, len ) ) >= 0 ) {
+
+                       /* Default to string type, if not yet specified */
+                       if ( ! tmp.type )
+                               tmp.type = &setting_type_string;
+
+                       /* Record origin, if applicable */
+                       if ( origin )
+                               *origin = settings;
+
+                       /* Record fetched setting, if applicable */
+                       if ( fetched )
+                               memcpy ( fetched, &tmp, sizeof ( *fetched ) );
+
+                       return ret;
+               }
+       }
+
+       /* Recurse into each child block in turn */
+       list_for_each_entry ( child, &settings->children, siblings ) {
+               if ( ( ret = fetch_setting ( child, setting, origin, fetched,
+                                            data, len ) ) >= 0 )
+                       return ret;
+       }
+
+       return -ENOENT;
+}
+
+/**
+ * Fetch allocated copy of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v origin           Origin of setting to fill in, or NULL
+ * @v fetched          Fetched setting to fill in, or NULL
+ * @v data             Buffer to allocate and fill with setting data
+ * @v alloc            Allocation function
+ * @ret len            Length of setting, or negative error
+ *
+ * The caller is responsible for eventually freeing the allocated
+ * buffer.
+ */
+static int fetch_setting_alloc ( struct settings *settings,
+                                const struct setting *setting,
+                                struct settings **origin,
+                                struct setting *fetched,
+                                void **data,
+                                void * ( * alloc ) ( size_t len ) ) {
+       struct settings *tmp_origin;
+       struct setting tmp_fetched;
+       int len;
+       int check_len;
+
+       /* Use local buffers if necessary */
+       if ( ! origin )
+               origin = &tmp_origin;
+       if ( ! fetched )
+               fetched = &tmp_fetched;
+
+       /* Avoid returning uninitialised data on error */
+       *data = NULL;
+
+       /* Check existence, and fetch setting length */
+       len = fetch_setting ( settings, setting, origin, fetched, NULL, 0 );
+       if ( len < 0 )
+               return len;
+
+       /* Allocate buffer */
+       *data = alloc ( len );
+       if ( ! *data )
+               return -ENOMEM;
+
+       /* Fetch setting value */
+       check_len = fetch_setting ( *origin, fetched, NULL, NULL, *data, len );
+       assert ( check_len == len );
+       return len;
+}
+
+/**
+ * Fetch copy of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v origin           Origin of setting to fill in, or NULL
+ * @v fetched          Fetched setting to fill in, or NULL
+ * @v data             Buffer to allocate and fill with setting data
+ * @ret len            Length of setting, or negative error
+ *
+ * The caller is responsible for eventually freeing the allocated
+ * buffer.
+ */
+int fetch_setting_copy ( struct settings *settings,
+                        const struct setting *setting,
+                        struct settings **origin, struct setting *fetched,
+                        void **data ) {
+
+       return fetch_setting_alloc ( settings, setting, origin, fetched,
+                                    data, malloc );
+}
+
+/**
+ * Fetch value of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v data             Buffer to fill with setting string data
+ * @v len              Length of buffer
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_raw_setting ( struct settings *settings,
+                       const struct setting *setting,
+                       void *data, size_t len ) {
+
+       return fetch_setting ( settings, setting, NULL, NULL, data, len );
+}
+
+/**
+ * Fetch value of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v data             Buffer to allocate and fill with setting data
+ * @ret len            Length of setting, or negative error
+ *
+ * The caller is responsible for eventually freeing the allocated
+ * buffer.
+ */
+int fetch_raw_setting_copy ( struct settings *settings,
+                            const struct setting *setting,
+                            void **data ) {
+
+       return fetch_setting_copy ( settings, setting, NULL, NULL, data );
+}
+
+/**
+ * Fetch value of string setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v data             Buffer to fill with setting string data
+ * @v len              Length of buffer
+ * @ret len            Length of string setting, or negative error
+ *
+ * The resulting string is guaranteed to be correctly NUL-terminated.
+ * The returned length will be the length of the underlying setting
+ * data.
+ */
+int fetch_string_setting ( struct settings *settings,
+                          const struct setting *setting,
+                          char *data, size_t len ) {
+
+       memset ( data, 0, len );
+       return fetch_raw_setting ( settings, setting, data,
+                                  ( ( len > 0 ) ? ( len - 1 ) : 0 ) );
+}
+
+/**
+ * Allocate memory for copy of string setting
+ *
+ * @v len              Length of setting
+ * @ret ptr            Allocated memory
+ */
+static void * fetch_string_setting_copy_alloc ( size_t len ) {
+       return zalloc ( len + 1 /* NUL */ );
+}
+
+/**
+ * Fetch value of string setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v data             Buffer to allocate and fill with setting string data
+ * @ret len            Length of string setting, or negative error
+ *
+ * The resulting string is guaranteed to be correctly NUL-terminated.
+ * The returned length will be the length of the underlying setting
+ * data.  The caller is responsible for eventually freeing the
+ * allocated buffer.
+ */
+int fetch_string_setting_copy ( struct settings *settings,
+                               const struct setting *setting, char **data ) {
+
+       return fetch_setting_alloc ( settings, setting, NULL, NULL,
+                                    ( ( void ** ) data ),
+                                    fetch_string_setting_copy_alloc );
+}
+
+/**
+ * Fetch value of IPv4 address setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v inp              IPv4 addresses to fill in
+ * @v count            Maximum number of IPv4 addresses
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_ipv4_array_setting ( struct settings *settings,
+                              const struct setting *setting,
+                              struct in_addr *inp, unsigned int count ) {
+       int len;
+
+       len = fetch_raw_setting ( settings, setting, inp,
+                                 ( sizeof ( *inp ) * count ) );
+       if ( len < 0 )
+               return len;
+       if ( ( len % sizeof ( *inp ) ) != 0 )
+               return -ERANGE;
+       return len;
+}
+
+/**
+ * Fetch value of IPv4 address setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v inp              IPv4 address to fill in
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_ipv4_setting ( struct settings *settings,
+                        const struct setting *setting,
+                        struct in_addr *inp ) {
+
+       return fetch_ipv4_array_setting ( settings, setting, inp, 1 );
+}
+
+/**
+ * Fetch value of IPv6 address setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v inp              IPv6 addresses to fill in
+ * @v count            Maximum number of IPv6 addresses
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_ipv6_array_setting ( struct settings *settings,
+                              const struct setting *setting,
+                              struct in6_addr *inp, unsigned int count ) {
+       int len;
+
+       len = fetch_raw_setting ( settings, setting, inp,
+                                 ( sizeof ( *inp ) * count ) );
+       if ( len < 0 )
+               return len;
+       if ( ( len % sizeof ( *inp ) ) != 0 )
+               return -ERANGE;
+       return len;
+}
+
+/**
+ * Fetch value of IPv6 address setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v inp              IPv6 address to fill in
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_ipv6_setting ( struct settings *settings,
+                        const struct setting *setting,
+                        struct in6_addr *inp ) {
+
+       return fetch_ipv6_array_setting ( settings, setting, inp, 1 );
+}
+
+/**
+ * Extract numeric value of setting
+ *
+ * @v is_signed                Treat value as a signed integer
+ * @v raw              Raw setting data
+ * @v len              Length of raw setting data
+ * @ret value          Numeric value
+ * @ret len            Length of setting, or negative error
+ */
+static int numeric_setting_value ( int is_signed, const void *raw, size_t len,
+                                  unsigned long *value ) {
+       const uint8_t *unsigned_bytes = raw;
+       const int8_t *signed_bytes = raw;
+       int is_negative;
+       unsigned int i;
+       uint8_t pad;
+       uint8_t byte;
+
+       /* Convert to host-ordered longs */
+       is_negative = ( len && ( signed_bytes[0] < 0 ) );
+       *value = ( ( is_signed && is_negative ) ? -1L : 0 );
+       pad = *value;
+       for ( i = 0 ; i < len ; i++ ) {
+               byte = unsigned_bytes[i];
+               *value = ( ( *value << 8 ) | byte );
+               if ( ( ( i + sizeof ( *value ) ) < len ) && ( byte != pad ) )
+                       return -ERANGE;
+       }
+
+       return len;
+}
+
+/**
+ * Fetch value of numeric setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v value            Integer value to fill in
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_numeric_setting ( struct settings *settings,
+                           const struct setting *setting,
+                           unsigned long *value, int is_signed ) {
+       unsigned long tmp;
+       int len;
+
+       /* Avoid returning uninitialised data on error */
+       *value = 0;
+
+       /* Fetch raw (network-ordered, variable-length) setting */
+       len = fetch_raw_setting ( settings, setting, &tmp, sizeof ( tmp ) );
+       if ( len < 0 )
+               return len;
+
+       /* Extract numeric value */
+       return numeric_setting_value ( is_signed, &tmp, len, value );
+}
+
+/**
+ * Fetch value of signed integer setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v value            Integer value to fill in
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_int_setting ( struct settings *settings,
+                       const struct setting *setting,
+                       long *value ) {
+
+       return fetch_numeric_setting ( settings, setting,
+                                      ( ( unsigned long * ) value ), 1 );
+}
+
+/**
+ * Fetch value of unsigned integer setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v value            Integer value to fill in
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_uint_setting ( struct settings *settings,
+                        const struct setting *setting,
+                        unsigned long *value ) {
+
+       return fetch_numeric_setting ( settings, setting, value, 0 );
+}
+
+/**
+ * Fetch value of signed integer setting, or zero
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @ret value          Setting value, or zero
+ */
+long fetch_intz_setting ( struct settings *settings,
+                         const struct setting *setting ) {
+       unsigned long value;
+
+       fetch_numeric_setting ( settings, setting, &value, 1 );
+       return value;
+}
+
+/**
+ * Fetch value of unsigned integer setting, or zero
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @ret value          Setting value, or zero
+ */
+unsigned long fetch_uintz_setting ( struct settings *settings,
+                                   const struct setting *setting ) {
+       unsigned long value;
+
+       fetch_numeric_setting ( settings, setting, &value, 0 );
+       return value;
+}
+
+/**
+ * Fetch value of UUID setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v uuid             UUID to fill in
+ * @ret len            Length of setting, or negative error
+ */
+int fetch_uuid_setting ( struct settings *settings,
+                        const struct setting *setting,
+                        union uuid *uuid ) {
+       int len;
+
+       len = fetch_raw_setting ( settings, setting, uuid, sizeof ( *uuid ) );
+       if ( len < 0 )
+               return len;
+       if ( len != sizeof ( *uuid ) )
+               return -ERANGE;
+       return len;
+}
+
+/**
+ * Clear settings block
+ *
+ * @v settings         Settings block
+ */
+void clear_settings ( struct settings *settings ) {
+
+       /* Find target settings block */
+       settings = settings_target ( settings );
+
+       /* Clear settings, if applicable */
+       if ( settings->op->clear )
+               settings->op->clear ( settings );
+}
+
+/**
+ * Compare two settings
+ *
+ * @v a                        Setting to compare
+ * @v b                        Setting to compare
+ * @ret 0              Settings are the same
+ * @ret non-zero       Settings are not the same
+ */
+int setting_cmp ( const struct setting *a, const struct setting *b ) {
+
+       /* If the settings have tags, compare them */
+       if ( a->tag && ( a->tag == b->tag ) && ( a->scope == b->scope ) )
+               return 0;
+
+       /* Otherwise, if the settings have names, compare them */
+       if ( a->name && b->name && a->name[0] )
+               return strcmp ( a->name, b->name );
+
+       /* Otherwise, return a non-match */
+       return ( ! 0 );
+}
+
+/******************************************************************************
+ *
+ * Formatted setting routines
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Format setting value as a string
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+int setting_format ( const struct setting_type *type, const void *raw,
+                    size_t raw_len, char *buf, size_t len ) {
+
+       /* Sanity check */
+       if ( ! type->format )
+               return -ENOTSUP;
+
+       return type->format ( type, raw, raw_len, buf, len );
+}
+
+/**
+ * Parse formatted string to setting value
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+int setting_parse ( const struct setting_type *type, const char *value,
+                   void *buf, size_t len ) {
+
+       /* Sanity check */
+       if ( ! type->parse )
+               return -ENOTSUP;
+
+       return type->parse ( type, value, buf, len );
+}
+
+/**
+ * Convert setting value to number
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @ret value          Numeric value
+ * @ret rc             Return status code
+ */
+int setting_numerate ( const struct setting_type *type, const void *raw,
+                      size_t raw_len, unsigned long *value ) {
+
+       /* Sanity check */
+       if ( ! type->numerate )
+               return -ENOTSUP;
+
+       return type->numerate ( type, raw, raw_len, value );
+}
+
+/**
+ * Convert number to setting value
+ *
+ * @v type             Setting type
+ * @v value            Numeric value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+int setting_denumerate ( const struct setting_type *type, unsigned long value,
+                        void *buf, size_t len ) {
+
+       /* Sanity check */
+       if ( ! type->denumerate )
+               return -ENOTSUP;
+
+       return type->denumerate ( type, value, buf, len );
+}
+
+/**
+ * Fetch formatted value of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v origin           Origin of setting to fill in, or NULL
+ * @v fetched          Fetched setting to fill in, or NULL
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+int fetchf_setting ( struct settings *settings, const struct setting *setting,
+                    struct settings **origin, struct setting *fetched,
+                    char *buf, size_t len ) {
+       struct setting tmp_fetched;
+       void *raw;
+       int raw_len;
+       int ret;
+
+       /* Use local buffers if necessary */
+       if ( ! fetched )
+               fetched = &tmp_fetched;
+
+       /* Fetch raw value */
+       raw_len = fetch_setting_copy ( settings, setting, origin, fetched,
+                                      &raw );
+       if ( raw_len < 0 ) {
+               ret = raw_len;
+               goto err_fetch_copy;
+       }
+
+       /* Sanity check */
+       assert ( fetched->type != NULL );
+
+       /* Format setting */
+       if ( ( ret = setting_format ( fetched->type, raw, raw_len, buf,
+                                     len ) ) < 0 )
+               goto err_format;
+
+ err_format:
+       free ( raw );
+ err_fetch_copy:
+       return ret;
+}
+
+/**
+ * Fetch copy of formatted value of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v origin           Origin of setting to fill in, or NULL
+ * @v fetched          Fetched setting to fill in, or NULL
+ * @v value            Buffer to allocate and fill with formatted value
+ * @ret len            Length of formatted value, or negative error
+ *
+ * The caller is responsible for eventually freeing the allocated
+ * buffer.
+ */
+int fetchf_setting_copy ( struct settings *settings,
+                         const struct setting *setting,
+                         struct settings **origin, struct setting *fetched,
+                         char **value ) {
+       struct settings *tmp_origin;
+       struct setting tmp_fetched;
+       int len;
+       int check_len;
+
+       /* Use local buffers if necessary */
+       if ( ! origin )
+               origin = &tmp_origin;
+       if ( ! fetched )
+               fetched = &tmp_fetched;
+
+       /* Avoid returning uninitialised data on error */
+       *value = NULL;
+
+       /* Check existence, and fetch formatted value length */
+       len = fetchf_setting ( settings, setting, origin, fetched, NULL, 0 );
+       if ( len < 0 )
+               return len;
+
+       /* Allocate buffer */
+       *value = zalloc ( len + 1 /* NUL */ );
+       if ( ! *value )
+               return -ENOMEM;
+
+       /* Fetch formatted value */
+       check_len = fetchf_setting ( *origin, fetched, NULL, NULL, *value,
+                                    ( len + 1 /* NUL */ ) );
+       assert ( check_len == len );
+       return len;
+}
+
+/**
+ * Store formatted value of setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting to store
+ * @v value            Formatted setting data, or NULL
+ * @ret rc             Return status code
+ */
+int storef_setting ( struct settings *settings, const struct setting *setting,
+                    const char *value ) {
+       void *raw;
+       int raw_len;
+       int check_len;
+       int rc;
+
+       /* NULL value or empty string implies deletion */
+       if ( ( ! value ) || ( ! value[0] ) )
+               return delete_setting ( settings, setting );
+
+       /* Sanity check */
+       assert ( setting->type != NULL );
+
+       /* Get raw value length */
+       raw_len = setting_parse ( setting->type, value, NULL, 0 );
+       if ( raw_len < 0 ) {
+               rc = raw_len;
+               goto err_raw_len;
+       }
+
+       /* Allocate buffer for raw value */
+       raw = malloc ( raw_len );
+       if ( ! raw ) {
+               rc = -ENOMEM;
+               goto err_alloc_raw;
+       }
+
+       /* Parse formatted value */
+       check_len = setting_parse ( setting->type, value, raw, raw_len );
+       assert ( check_len == raw_len );
+
+       /* Store raw value */
+       if ( ( rc = store_setting ( settings, setting, raw, raw_len ) ) != 0 )
+               goto err_store;
+
+ err_store:
+       free ( raw );
+ err_alloc_raw:
+ err_raw_len:
+       return rc;
+}
+
+/**
+ * Fetch numeric value of setting
+ *
+ * @v settings         Settings block, or NULL to search all blocks
+ * @v setting          Setting to fetch
+ * @v origin           Origin of setting to fill in, or NULL
+ * @v fetched          Fetched setting to fill in, or NULL
+ * @v value            Numeric value to fill in
+ * @ret rc             Return status code
+ */
+int fetchn_setting ( struct settings *settings, const struct setting *setting,
+                    struct settings **origin, struct setting *fetched,
+                    unsigned long *value ) {
+       struct setting tmp_fetched;
+       void *raw;
+       int raw_len;
+       int rc;
+
+       /* Use local buffers if necessary */
+       if ( ! fetched )
+               fetched = &tmp_fetched;
+
+       /* Fetch raw value */
+       raw_len = fetch_setting_copy ( settings, setting, origin, fetched,
+                                      &raw );
+       if ( raw_len < 0 ) {
+               rc = raw_len;
+               goto err_fetch_copy;
+       }
+
+       /* Sanity check */
+       assert ( fetched->type != NULL );
+
+       /* Numerate setting */
+       if ( ( rc = setting_numerate ( fetched->type, raw, raw_len,
+                                      value ) ) < 0 )
+               goto err_numerate;
+
+ err_numerate:
+       free ( raw );
+ err_fetch_copy:
+       return rc;
+}
+
+/**
+ * Store numeric value of setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting
+ * @v value            Numeric value
+ * @ret rc             Return status code
+ */
+int storen_setting ( struct settings *settings, const struct setting *setting,
+                    unsigned long value ) {
+       void *raw;
+       int raw_len;
+       int check_len;
+       int rc;
+
+       /* Sanity check */
+       assert ( setting->type != NULL );
+
+       /* Get raw value length */
+       raw_len = setting_denumerate ( setting->type, value, NULL, 0 );
+       if ( raw_len < 0 ) {
+               rc = raw_len;
+               goto err_raw_len;
+       }
+
+       /* Allocate buffer for raw value */
+       raw = malloc ( raw_len );
+       if ( ! raw ) {
+               rc = -ENOMEM;
+               goto err_alloc_raw;
+       }
+
+       /* Denumerate value */
+       check_len = setting_denumerate ( setting->type, value, raw, raw_len );
+       assert ( check_len == raw_len );
+
+       /* Store raw value */
+       if ( ( rc = store_setting ( settings, setting, raw, raw_len ) ) != 0 )
+               goto err_store;
+
+ err_store:
+       free ( raw );
+ err_alloc_raw:
+ err_raw_len:
+       return rc;
+}
+
+/******************************************************************************
+ *
+ * Named settings
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Find predefined setting
+ *
+ * @v name             Name
+ * @ret setting                Setting, or NULL
+ */
+struct setting * find_setting ( const char *name ) {
+       struct setting *setting;
+
+       for_each_table_entry ( setting, SETTINGS ) {
+               if ( strcmp ( name, setting->name ) == 0 )
+                       return setting;
+       }
+       return NULL;
+}
+
+/**
+ * Parse setting name as tag number
+ *
+ * @v name             Name
+ * @ret tag            Tag number, or 0 if not a valid number
+ */
+static unsigned int parse_setting_tag ( const char *name ) {
+       char *tmp = ( ( char * ) name );
+       unsigned int tag = 0;
+
+       while ( 1 ) {
+               tag = ( ( tag << 8 ) | strtoul ( tmp, &tmp, 0 ) );
+               if ( *tmp == 0 )
+                       return tag;
+               if ( *tmp != '.' )
+                       return 0;
+               tmp++;
+       }
+}
+
+/**
+ * Find setting type
+ *
+ * @v name             Name
+ * @ret type           Setting type, or NULL
+ */
+static const struct setting_type * find_setting_type ( const char *name ) {
+       const struct setting_type *type;
+
+       for_each_table_entry ( type, SETTING_TYPES ) {
+               if ( strcmp ( name, type->name ) == 0 )
+                       return type;
+       }
+       return NULL;
+}
+
+/**
+ * Parse setting name
+ *
+ * @v name             Name of setting
+ * @v get_child                Function to find or create child settings block
+ * @v settings         Settings block to fill in
+ * @v setting          Setting to fill in
+ * @ret rc             Return status code
+ *
+ * Interprets a name of the form
+ * "[settings_name/]tag_name[:type_name]" and fills in the appropriate
+ * fields.
+ *
+ * Note that on success, this function will have modified the original
+ * setting @c name.
+ */
+int parse_setting_name ( char *name, get_child_settings_t get_child,
+                        struct settings **settings, struct setting *setting ) {
+       char *settings_name;
+       char *setting_name;
+       char *type_name;
+       struct setting *predefined;
+       int rc;
+
+       /* Set defaults */
+       *settings = &settings_root;
+       memset ( setting, 0, sizeof ( *setting ) );
+       setting->name = "";
+
+       /* Split name into "[settings_name/]setting_name[:type_name]" */
+       if ( ( setting_name = strchr ( name, '/' ) ) != NULL ) {
+               *(setting_name++) = 0;
+               settings_name = name;
+       } else {
+               setting_name = name;
+               settings_name = NULL;
+       }
+       if ( ( type_name = strchr ( setting_name, ':' ) ) != NULL )
+               *(type_name++) = 0;
+
+       /* Identify settings block, if specified */
+       if ( settings_name ) {
+               *settings = parse_settings_name ( settings_name, get_child );
+               if ( *settings == NULL ) {
+                       DBG ( "Unrecognised settings block \"%s\" in \"%s\"\n",
+                             settings_name, name );
+                       rc = -ENODEV;
+                       goto err;
+               }
+       }
+
+       /* Identify setting */
+       setting->tag = parse_setting_tag ( setting_name );
+       setting->scope = (*settings)->default_scope;
+       setting->name = setting_name;
+       for_each_table_entry ( predefined, SETTINGS ) {
+               /* Matches a predefined setting; use that setting */
+               if ( setting_cmp ( predefined, setting ) == 0 ) {
+                       memcpy ( setting, predefined, sizeof ( *setting ) );
+                       break;
+               }
+       }
+
+       /* Identify setting type, if specified */
+       if ( type_name ) {
+               setting->type = find_setting_type ( type_name );
+               if ( setting->type == NULL ) {
+                       DBG ( "Invalid setting type \"%s\" in \"%s\"\n",
+                             type_name, name );
+                       rc = -ENOTSUP;
+                       goto err;
+               }
+       }
+
+       return 0;
+
+ err:
+       /* Restore original name */
+       if ( settings_name )
+               *( setting_name - 1 ) = '/';
+       if ( type_name )
+               *( type_name - 1 ) = ':';
+       return rc;
+}
+
+/**
+ * Return full setting name
+ *
+ * @v settings         Settings block, or NULL
+ * @v setting          Setting
+ * @v buf              Buffer
+ * @v len              Length of buffer
+ * @ret len            Length of setting name, or negative error
+ */
+int setting_name ( struct settings *settings, const struct setting *setting,
+                  char *buf, size_t len ) {
+       const char *name;
+
+       settings = settings_target ( settings );
+       name = settings_name ( settings );
+       return snprintf ( buf, len, "%s%s%s:%s", name, ( name[0] ? "/" : "" ),
+                         setting->name, setting->type->name );
+}
+
+/******************************************************************************
+ *
+ * Setting types
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Parse string setting value
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+static int parse_string_setting ( const struct setting_type *type __unused,
+                                 const char *value, void *buf, size_t len ) {
+       size_t raw_len = strlen ( value ); /* Exclude terminating NUL */
+
+       /* Copy string to buffer */
+       if ( len > raw_len )
+               len = raw_len;
+       memcpy ( buf, value, len );
+
+       return raw_len;
+}
+
+/**
+ * Format string setting value
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_string_setting ( const struct setting_type *type __unused,
+                                  const void *raw, size_t raw_len, char *buf,
+                                  size_t len ) {
+
+       /* Copy string to buffer, and terminate */
+       memset ( buf, 0, len );
+       if ( len > raw_len )
+               len = raw_len;
+       memcpy ( buf, raw, len );
+
+       return raw_len;
+}
+
+/** A string setting type */
+const struct setting_type setting_type_string __setting_type = {
+       .name = "string",
+       .parse = parse_string_setting,
+       .format = format_string_setting,
+};
+
+/** A URI-encoded string setting type
+ *
+ * This setting type is obsolete; the name ":uristring" is retained to
+ * avoid breaking existing scripts.
+ */
+const struct setting_type setting_type_uristring __setting_type = {
+       .name = "uristring",
+       .parse = parse_string_setting,
+       .format = format_string_setting,
+};
+
+/**
+ * Parse IPv4 address setting value (when IPv4 support is not present)
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+__weak int parse_ipv4_setting ( const struct setting_type *type __unused,
+                               const char *value __unused, void *buf __unused,
+                               size_t len __unused ) {
+       return -ENOTSUP;
+}
+
+/**
+ * Format IPv4 address setting value (when IPv4 support is not present)
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+__weak int format_ipv4_setting ( const struct setting_type *type __unused,
+                                const void *raw __unused,
+                                size_t raw_len __unused, char *buf __unused,
+                                size_t len __unused ) {
+       return -ENOTSUP;
+}
+
+/** An IPv4 address setting type */
+const struct setting_type setting_type_ipv4 __setting_type = {
+       .name = "ipv4",
+       .parse = parse_ipv4_setting,
+       .format = format_ipv4_setting,
+};
+
+/**
+ * Parse IPv6 address setting value (when IPv6 support is not present)
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+__weak int parse_ipv6_setting ( const struct setting_type *type __unused,
+                               const char *value __unused, void *buf __unused,
+                               size_t len __unused ) {
+       return -ENOTSUP;
+}
+
+/**
+ * Format IPv6 address setting value (when IPv6 support is not present)
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+__weak int format_ipv6_setting ( const struct setting_type *type __unused,
+                                const void *raw __unused,
+                                size_t raw_len __unused, char *buf __unused,
+                                size_t len __unused ) {
+       return -ENOTSUP;
+}
+
+/** An IPv6 address setting type */
+const struct setting_type setting_type_ipv6 __setting_type = {
+       .name = "ipv6",
+       .parse = parse_ipv6_setting,
+       .format = format_ipv6_setting,
+};
+
+/** IPv6 settings scope */
+const struct settings_scope ipv6_scope;
+
+/**
+ * Integer setting type indices
+ *
+ * These indexes are defined such that (1<<index) gives the width of
+ * the integer, in bytes.
+ */
+enum setting_type_int_index {
+       SETTING_TYPE_INT8 = 0,
+       SETTING_TYPE_INT16 = 1,
+       SETTING_TYPE_INT32 = 2,
+};
+
+/**
+ * Integer setting type names
+ *
+ * These names exist as a static array in order to allow the type's
+ * integer size and signedness to be determined from the type's name.
+ * Note that there are no separate entries for the signed integer
+ * types: the name pointers simply point to the second character of
+ * the relevant string.
+ */
+static const char setting_type_int_name[][8] = {
+       [SETTING_TYPE_INT8] = "uint8",
+       [SETTING_TYPE_INT16] = "uint16",
+       [SETTING_TYPE_INT32] = "uint32",
+};
+
+/**
+ * Get unsigned integer setting type name
+ *
+ * @v index            Integer setting type index
+ * @ret name           Setting type name
+ */
+#define SETTING_TYPE_UINT_NAME( index ) setting_type_int_name[index]
+
+/**
+ * Get signed integer setting type name
+ *
+ * @v index            Integer setting type index
+ * @ret name           Setting type name
+ */
+#define SETTING_TYPE_INT_NAME( index ) ( setting_type_int_name[index] + 1 )
+
+/**
+ * Get integer setting type index
+ *
+ * @v type             Setting type
+ * @ret index          Integer setting type index
+ */
+static unsigned int setting_type_int_index ( const struct setting_type *type ) {
+
+       return ( ( type->name - setting_type_int_name[0] ) /
+                sizeof ( setting_type_int_name[0] ) );
+}
+
+/**
+ * Get integer setting type width
+ *
+ * @v type             Setting type
+ * @ret index          Integer setting type width
+ */
+static unsigned int setting_type_int_width ( const struct setting_type *type ) {
+
+       return ( 1 << setting_type_int_index ( type ) );
+}
+
+/**
+ * Get integer setting type signedness
+ *
+ * @v type             Setting type
+ * @ret is_signed      Integer setting type is signed
+ */
+static int setting_type_int_is_signed ( const struct setting_type *type ) {
+       return ( ( type->name - setting_type_int_name[0] ) & 1 );
+}
+
+/**
+ * Convert number to setting value
+ *
+ * @v type             Setting type
+ * @v value            Numeric value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+static int denumerate_int_setting ( const struct setting_type *type,
+                                   unsigned long value, void *buf,
+                                   size_t len ) {
+       unsigned int size = setting_type_int_width ( type );
+       union {
+               uint32_t num;
+               uint8_t bytes[4];
+       } u;
+
+       u.num = htonl ( value );
+       if ( len > size )
+               len = size;
+       memcpy ( buf, &u.bytes[ sizeof ( u ) - size ], len );
+
+       return size;
+}
+
+/**
+ * Convert setting value to number
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v value            Numeric value to fill in
+ * @ret rc             Return status code
+ */
+static int numerate_int_setting ( const struct setting_type *type,
+                                 const void *raw, size_t raw_len,
+                                 unsigned long *value ) {
+       int is_signed = setting_type_int_is_signed ( type );
+       int check_len;
+
+       /* Extract numeric value */
+       check_len = numeric_setting_value ( is_signed, raw, raw_len, value );
+       if ( check_len < 0 )
+               return check_len;
+       assert ( check_len == ( int ) raw_len );
+
+       return 0;
+}
+
+/**
+ * Parse integer setting value
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @ret len            Length of raw value, or negative error
+ */
+static int parse_int_setting ( const struct setting_type *type,
+                              const char *value, void *buf, size_t len ) {
+       char *endp;
+       unsigned long num_value;
+
+       /* Parse value */
+       num_value = strtoul ( value, &endp, 0 );
+       if ( *endp )
+               return -EINVAL;
+
+       return type->denumerate ( type, num_value, buf, len );
+}
+
+/**
+ * Format signed integer setting value
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_int_setting ( const struct setting_type *type,
+                               const void *raw, size_t raw_len,
+                               char *buf, size_t len ) {
+       unsigned long value;
+       int ret;
+
+       /* Extract numeric value */
+       if ( ( ret = type->numerate ( type, raw, raw_len, &value ) ) < 0 )
+               return ret;
+
+       /* Format value */
+       return snprintf ( buf, len, "%ld", value );
+}
+
+/**
+ * Format unsigned integer setting value
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_uint_setting ( const struct setting_type *type,
+                                const void *raw, size_t raw_len,
+                                char *buf, size_t len ) {
+       unsigned long value;
+       int ret;
+
+       /* Extract numeric value */
+       if ( ( ret = type->numerate ( type, raw, raw_len, &value ) ) < 0 )
+               return ret;
+
+       /* Format value */
+       return snprintf ( buf, len, "%#lx", value );
+}
+
+/**
+ * Define a signed integer setting type
+ *
+ * @v index            Integer setting type index
+ * @ret type           Setting type
+ */
+#define SETTING_TYPE_INT( index ) {                            \
+       .name = SETTING_TYPE_INT_NAME ( index ),                \
+       .parse = parse_int_setting,                             \
+       .format = format_int_setting,                           \
+       .denumerate = denumerate_int_setting,                   \
+       .numerate = numerate_int_setting,                       \
+}
+
+/**
+ * Define an unsigned integer setting type
+ *
+ * @v index            Integer setting type index
+ * @ret type           Setting type
+ */
+#define SETTING_TYPE_UINT( index ) {                           \
+       .name = SETTING_TYPE_UINT_NAME ( index ),               \
+       .parse = parse_int_setting,                             \
+       .format = format_uint_setting,                          \
+       .denumerate = denumerate_int_setting,                   \
+       .numerate = numerate_int_setting,                       \
+}
+
+/** A signed 8-bit integer setting type */
+const struct setting_type setting_type_int8 __setting_type =
+       SETTING_TYPE_INT ( SETTING_TYPE_INT8 );
+
+/** A signed 16-bit integer setting type */
+const struct setting_type setting_type_int16 __setting_type =
+       SETTING_TYPE_INT ( SETTING_TYPE_INT16 );
+
+/** A signed 32-bit integer setting type */
+const struct setting_type setting_type_int32 __setting_type =
+       SETTING_TYPE_INT ( SETTING_TYPE_INT32 );
+
+/** An unsigned 8-bit integer setting type */
+const struct setting_type setting_type_uint8 __setting_type =
+       SETTING_TYPE_UINT ( SETTING_TYPE_INT8 );
+
+/** An unsigned 16-bit integer setting type */
+const struct setting_type setting_type_uint16 __setting_type =
+       SETTING_TYPE_UINT ( SETTING_TYPE_INT16 );
+
+/** An unsigned 32-bit integer setting type */
+const struct setting_type setting_type_uint32 __setting_type =
+       SETTING_TYPE_UINT ( SETTING_TYPE_INT32 );
+
+/**
+ * Format hex string setting value
+ *
+ * @v delimiter                Byte delimiter
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_hex_setting ( const char *delimiter, const void *raw,
+                               size_t raw_len, char *buf, size_t len ) {
+       const uint8_t *bytes = raw;
+       int used = 0;
+       unsigned int i;
+
+       if ( len )
+               buf[0] = 0; /* Ensure that a terminating NUL exists */
+       for ( i = 0 ; i < raw_len ; i++ ) {
+               used += ssnprintf ( ( buf + used ), ( len - used ),
+                                   "%s%02x", ( used ? delimiter : "" ),
+                                   bytes[i] );
+       }
+       return used;
+}
+
+/**
+ * Parse hex string setting value (using colon delimiter)
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @v size             Integer size, in bytes
+ * @ret len            Length of raw value, or negative error
+ */
+static int parse_hex_setting ( const struct setting_type *type __unused,
+                              const char *value, void *buf, size_t len ) {
+       return hex_decode ( value, ':', buf, len );
+}
+
+/**
+ * Format hex string setting value (using colon delimiter)
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_hex_colon_setting ( const struct setting_type *type __unused,
+                                     const void *raw, size_t raw_len,
+                                     char *buf, size_t len ) {
+       return format_hex_setting ( ":", raw, raw_len, buf, len );
+}
+
+/**
+ * Parse hex string setting value (using hyphen delimiter)
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @v size             Integer size, in bytes
+ * @ret len            Length of raw value, or negative error
+ */
+static int parse_hex_hyphen_setting ( const struct setting_type *type __unused,
+                                     const char *value, void *buf,
+                                     size_t len ) {
+       return hex_decode ( value, '-', buf, len );
+}
+
+/**
+ * Format hex string setting value (using hyphen delimiter)
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_hex_hyphen_setting ( const struct setting_type *type __unused,
+                                      const void *raw, size_t raw_len,
+                                      char *buf, size_t len ) {
+       return format_hex_setting ( "-", raw, raw_len, buf, len );
+}
+
+/**
+ * Parse hex string setting value (using no delimiter)
+ *
+ * @v type             Setting type
+ * @v value            Formatted setting value
+ * @v buf              Buffer to contain raw value
+ * @v len              Length of buffer
+ * @v size             Integer size, in bytes
+ * @ret len            Length of raw value, or negative error
+ */
+static int parse_hex_raw_setting ( const struct setting_type *type __unused,
+                                  const char *value, void *buf, size_t len ) {
+       return hex_decode ( value, 0, buf, len );
+}
+
+/**
+ * Format hex string setting value (using no delimiter)
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_hex_raw_setting ( const struct setting_type *type __unused,
+                                   const void *raw, size_t raw_len,
+                                   char *buf, size_t len ) {
+       return format_hex_setting ( "", raw, raw_len, buf, len );
+}
+
+/** A hex-string setting (colon-delimited) */
+const struct setting_type setting_type_hex __setting_type = {
+       .name = "hex",
+       .parse = parse_hex_setting,
+       .format = format_hex_colon_setting,
+};
+
+/** A hex-string setting (hyphen-delimited) */
+const struct setting_type setting_type_hexhyp __setting_type = {
+       .name = "hexhyp",
+       .parse = parse_hex_hyphen_setting,
+       .format = format_hex_hyphen_setting,
+};
+
+/** A hex-string setting (non-delimited) */
+const struct setting_type setting_type_hexraw __setting_type = {
+       .name = "hexraw",
+       .parse = parse_hex_raw_setting,
+       .format = format_hex_raw_setting,
+};
+
+/**
+ * Format UUID setting value
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_uuid_setting ( const struct setting_type *type __unused,
+                                const void *raw, size_t raw_len, char *buf,
+                                size_t len ) {
+       const union uuid *uuid = raw;
+
+       /* Range check */
+       if ( raw_len != sizeof ( *uuid ) )
+               return -ERANGE;
+
+       /* Format value */
+       return snprintf ( buf, len, "%s", uuid_ntoa ( uuid ) );
+}
+
+/** UUID setting type */
+const struct setting_type setting_type_uuid __setting_type = {
+       .name = "uuid",
+       .format = format_uuid_setting,
+};
+
+/**
+ * Format PCI bus:dev.fn setting value
+ *
+ * @v type             Setting type
+ * @v raw              Raw setting value
+ * @v raw_len          Length of raw setting value
+ * @v buf              Buffer to contain formatted value
+ * @v len              Length of buffer
+ * @ret len            Length of formatted value, or negative error
+ */
+static int format_busdevfn_setting ( const struct setting_type *type __unused,
+                                    const void *raw, size_t raw_len, char *buf,
+                                    size_t len ) {
+       unsigned long busdevfn;
+       int check_len;
+
+       /* Extract numeric value */
+       check_len = numeric_setting_value ( 0, raw, raw_len, &busdevfn );
+       if ( check_len < 0 )
+               return check_len;
+       assert ( check_len == ( int ) raw_len );
+
+       /* Format value */
+       return snprintf ( buf, len, "%02lx:%02lx.%lx", PCI_BUS ( busdevfn ),
+                         PCI_SLOT ( busdevfn ), PCI_FUNC ( busdevfn ) );
+}
+
+/** PCI bus:dev.fn setting type */
+const struct setting_type setting_type_busdevfn __setting_type = {
+       .name = "busdevfn",
+       .format = format_busdevfn_setting,
+};
+
+/******************************************************************************
+ *
+ * Setting expansion
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Expand variables within string
+ *
+ * @v string           String
+ * @ret expstr         Expanded string
+ *
+ * The expanded string is allocated with malloc() and the caller must
+ * eventually free() it.
+ */
+char * expand_settings ( const char *string ) {
+       struct settings *settings;
+       struct setting setting;
+       char *expstr;
+       char *start;
+       char *end;
+       char *head;
+       char *name;
+       char *tail;
+       char *value;
+       char *tmp;
+       int new_len;
+       int rc;
+
+       /* Obtain temporary modifiable copy of string */
+       expstr = strdup ( string );
+       if ( ! expstr )
+               return NULL;
+
+       /* Expand while expansions remain */
+       while ( 1 ) {
+
+               head = expstr;
+
+               /* Locate setting to be expanded */
+               start = NULL;
+               end = NULL;
+               for ( tmp = expstr ; *tmp ; tmp++ ) {
+                       if ( ( tmp[0] == '$' ) && ( tmp[1] == '{' ) )
+                               start = tmp;
+                       if ( start && ( tmp[0] == '}' ) ) {
+                               end = tmp;
+                               break;
+                       }
+               }
+               if ( ! end )
+                       break;
+               *start = '\0';
+               name = ( start + 2 );
+               *end = '\0';
+               tail = ( end + 1 );
+
+               /* Expand setting */
+               if ( ( rc = parse_setting_name ( name, find_child_settings,
+                                                &settings,
+                                                &setting ) ) != 0 ) {
+                       /* Treat invalid setting names as empty */
+                       value = NULL;
+               } else {
+                       /* Fetch and format setting value.  Ignore
+                        * errors; treat non-existent settings as empty.
+                        */
+                       fetchf_setting_copy ( settings, &setting, NULL, NULL,
+                                             &value );
+               }
+
+               /* Construct expanded string and discard old string */
+               tmp = expstr;
+               new_len = asprintf ( &expstr, "%s%s%s",
+                                    head, ( value ? value : "" ), tail );
+               free ( value );
+               free ( tmp );
+               if ( new_len < 0 )
+                       return NULL;
+       }
+
+       return expstr;
+}
+
+/******************************************************************************
+ *
+ * Settings
+ *
+ ******************************************************************************
+ */
+
+/** Hostname setting */
+const struct setting hostname_setting __setting ( SETTING_HOST, hostname ) = {
+       .name = "hostname",
+       .description = "Host name",
+       .tag = DHCP_HOST_NAME,
+       .type = &setting_type_string,
+};
+
+/** Domain name setting */
+const struct setting domain_setting __setting ( SETTING_IP_EXTRA, domain ) = {
+       .name = "domain",
+       .description = "DNS domain",
+       .tag = DHCP_DOMAIN_NAME,
+       .type = &setting_type_string,
+};
+
+/** TFTP server setting */
+const struct setting next_server_setting __setting ( SETTING_BOOT,next-server)={
+       .name = "next-server",
+       .description = "TFTP server",
+       .tag = DHCP_EB_SIADDR,
+       .type = &setting_type_ipv4,
+};
+
+/** Filename setting */
+const struct setting filename_setting __setting ( SETTING_BOOT, filename ) = {
+       .name = "filename",
+       .description = "Boot filename",
+       .tag = DHCP_BOOTFILE_NAME,
+       .type = &setting_type_string,
+};
+
+/** Root path setting */
+const struct setting root_path_setting __setting ( SETTING_SANBOOT, root-path)={
+       .name = "root-path",
+       .description = "SAN root path",
+       .tag = DHCP_ROOT_PATH,
+       .type = &setting_type_string,
+};
+
+/** Username setting */
+const struct setting username_setting __setting ( SETTING_AUTH, username ) = {
+       .name = "username",
+       .description = "User name",
+       .tag = DHCP_EB_USERNAME,
+       .type = &setting_type_string,
+};
+
+/** Password setting */
+const struct setting password_setting __setting ( SETTING_AUTH, password ) = {
+       .name = "password",
+       .description = "Password",
+       .tag = DHCP_EB_PASSWORD,
+       .type = &setting_type_string,
+};
+
+/** Priority setting */
+const struct setting priority_setting __setting ( SETTING_MISC, priority ) = {
+       .name = "priority",
+       .description = "Settings priority",
+       .tag = DHCP_EB_PRIORITY,
+       .type = &setting_type_int8,
+};
+
+/** DHCP user class setting */
+const struct setting user_class_setting __setting ( SETTING_HOST_EXTRA,
+                                                   user-class ) = {
+       .name = "user-class",
+       .description = "DHCP user class",
+       .tag = DHCP_USER_CLASS_ID,
+       .type = &setting_type_string,
+};
+
+/******************************************************************************
+ *
+ * Built-in settings block
+ *
+ ******************************************************************************
+ */
+
+/** Built-in setting scope */
+const struct settings_scope builtin_scope;
+
+/**
+ * Fetch error number setting
+ *
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ */
+static int errno_fetch ( void *data, size_t len ) {
+       uint32_t content;
+
+       /* Return current error */
+       content = htonl ( errno );
+       if ( len > sizeof ( content ) )
+               len = sizeof ( content );
+       memcpy ( data, &content, len );
+       return sizeof ( content );
+}
+
+/** Error number setting */
+const struct setting errno_setting __setting ( SETTING_MISC, errno ) = {
+       .name = "errno",
+       .description = "Last error",
+       .type = &setting_type_uint32,
+       .scope = &builtin_scope,
+};
+
+/** Error number built-in setting */
+struct builtin_setting errno_builtin_setting __builtin_setting = {
+       .setting = &errno_setting,
+       .fetch = errno_fetch,
+};
+
+/**
+ * Fetch build architecture setting
+ *
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ */
+static int buildarch_fetch ( void *data, size_t len ) {
+       static const char buildarch[] = _S2 ( ARCH );
+
+       strncpy ( data, buildarch, len );
+       return ( sizeof ( buildarch ) - 1 /* NUL */ );
+}
+
+/** Build architecture setting */
+const struct setting buildarch_setting __setting ( SETTING_MISC, buildarch ) = {
+       .name = "buildarch",
+       .description = "Build architecture",
+       .type = &setting_type_string,
+       .scope = &builtin_scope,
+};
+
+/** Build architecture built-in setting */
+struct builtin_setting buildarch_builtin_setting __builtin_setting = {
+       .setting = &buildarch_setting,
+       .fetch = buildarch_fetch,
+};
+
+/**
+ * Fetch platform setting
+ *
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ */
+static int platform_fetch ( void *data, size_t len ) {
+       static const char platform[] = _S2 ( PLATFORM );
+
+       strncpy ( data, platform, len );
+       return ( sizeof ( platform ) - 1 /* NUL */ );
+}
+
+/** Platform setting */
+const struct setting platform_setting __setting ( SETTING_MISC, platform ) = {
+       .name = "platform",
+       .description = "Platform",
+       .type = &setting_type_string,
+       .scope = &builtin_scope,
+};
+
+/** Platform built-in setting */
+struct builtin_setting platform_builtin_setting __builtin_setting = {
+       .setting = &platform_setting,
+       .fetch = platform_fetch,
+};
+
+/**
+ * Fetch version setting
+ *
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ */
+static int version_fetch ( void *data, size_t len ) {
+       strncpy ( data, product_version, len );
+       return ( strlen ( product_version ) );
+}
+
+/** Version setting */
+const struct setting version_setting __setting ( SETTING_MISC, version ) = {
+       .name = "version",
+       .description = "Version",
+       .type = &setting_type_string,
+       .scope = &builtin_scope,
+};
+
+/** Version built-in setting */
+struct builtin_setting version_builtin_setting __builtin_setting = {
+       .setting = &version_setting,
+       .fetch = version_fetch,
+};
+
+/**
+ * Fetch built-in setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting to fetch
+ * @v data             Buffer to fill with setting data
+ * @v len              Length of buffer
+ * @ret len            Length of setting data, or negative error
+ */
+static int builtin_fetch ( struct settings *settings __unused,
+                          struct setting *setting,
+                          void *data, size_t len ) {
+       struct builtin_setting *builtin;
+
+       for_each_table_entry ( builtin, BUILTIN_SETTINGS ) {
+               if ( setting_cmp ( setting, builtin->setting ) == 0 )
+                       return builtin->fetch ( data, len );
+       }
+       return -ENOENT;
+}
+
+/**
+ * Check applicability of built-in setting
+ *
+ * @v settings         Settings block
+ * @v setting          Setting
+ * @ret applies                Setting applies within this settings block
+ */
+static int builtin_applies ( struct settings *settings __unused,
+                            const struct setting *setting ) {
+
+       return ( setting->scope == &builtin_scope );
+}
+
+/** Built-in settings operations */
+static struct settings_operations builtin_settings_operations = {
+       .applies = builtin_applies,
+       .fetch = builtin_fetch,
+};
+
+/** Built-in settings */
+static struct settings builtin_settings = {
+       .refcnt = NULL,
+       .siblings = LIST_HEAD_INIT ( builtin_settings.siblings ),
+       .children = LIST_HEAD_INIT ( builtin_settings.children ),
+       .op = &builtin_settings_operations,
+};
+
+/** Initialise built-in settings */
+static void builtin_init ( void ) {
+       int rc;
+
+       if ( ( rc = register_settings ( &builtin_settings, NULL,
+                                       "builtin" ) ) != 0 ) {
+               DBG ( "Could not register built-in settings: %s\n",
+                     strerror ( rc ) );
+               return;
+       }
+}
+
+/** Built-in settings initialiser */
+struct init_fn builtin_init_fn __init_fn ( INIT_NORMAL ) = {
+       .initialise = builtin_init,
+};