Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / drivers / staging / unisys / visorutil / charqueue.c

diff --git a/kernel/drivers/staging/unisys/visorutil/charqueue.c b/kernel/drivers/staging/unisys/visorutil/charqueue.c
new file mode 100644 (file)
index 0000000..c91752a
--- /dev/null
+++ b/kernel/drivers/staging/unisys/visorutil/charqueue.c
@@ -0,0 +1,127 @@
+/* charqueue.c
+ *
+ * Copyright (C) 2010 - 2013 UNISYS CORPORATION
+ * All rights reserved.
+ *
+ * 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 (at
+ * your option) 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, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ */
+
+/*
+ *  Simple character queue implementation for Linux kernel mode.
+ */
+
+#include "charqueue.h"
+
+#define MYDRVNAME "charqueue"
+
+#define IS_EMPTY(charqueue) (charqueue->head == charqueue->tail)
+
+struct charqueue {
+       int alloc_size;
+       int nslots;
+       spinlock_t lock; /* read/write lock for this structure */
+       int head, tail;
+       unsigned char buf[0];
+};
+
+struct charqueue *visor_charqueue_create(ulong nslots)
+{
+       int alloc_size = sizeof(struct charqueue) + nslots + 1;
+       struct charqueue *cq;
+
+       cq = kmalloc(alloc_size, GFP_KERNEL|__GFP_NORETRY);
+       if (cq == NULL)
+               return NULL;
+       cq->alloc_size = alloc_size;
+       cq->nslots = nslots;
+       cq->head = 0;
+       cq->tail = 0;
+       spin_lock_init(&cq->lock);
+       return cq;
+}
+EXPORT_SYMBOL_GPL(visor_charqueue_create);
+
+void visor_charqueue_enqueue(struct charqueue *charqueue, unsigned char c)
+{
+       int alloc_slots = charqueue->nslots+1;  /* 1 slot is always empty */
+
+       spin_lock(&charqueue->lock);
+       charqueue->head = (charqueue->head+1) % alloc_slots;
+       if (charqueue->head == charqueue->tail)
+               /* overflow; overwrite the oldest entry */
+               charqueue->tail = (charqueue->tail+1) % alloc_slots;
+       charqueue->buf[charqueue->head] = c;
+       spin_unlock(&charqueue->lock);
+}
+EXPORT_SYMBOL_GPL(visor_charqueue_enqueue);
+
+BOOL visor_charqueue_is_empty(struct charqueue *charqueue)
+{
+       BOOL b;
+
+       spin_lock(&charqueue->lock);
+       b = IS_EMPTY(charqueue);
+       spin_unlock(&charqueue->lock);
+       return b;
+}
+EXPORT_SYMBOL_GPL(visor_charqueue_is_empty);
+
+static int charqueue_dequeue_1(struct charqueue *charqueue)
+{
+       int alloc_slots = charqueue->nslots + 1;  /* 1 slot is always empty */
+
+       if (IS_EMPTY(charqueue))
+               return -1;
+       charqueue->tail = (charqueue->tail+1) % alloc_slots;
+       return charqueue->buf[charqueue->tail];
+}
+
+int charqueue_dequeue(struct charqueue *charqueue)
+{
+       int rc;
+
+       spin_lock(&charqueue->lock);
+       rc = charqueue_dequeue_1(charqueue);
+       spin_unlock(&charqueue->lock);
+       return rc;
+}
+
+int visor_charqueue_dequeue_n(struct charqueue *charqueue, unsigned char *buf,
+                             int n)
+{
+       int rc, counter = 0, c;
+
+       spin_lock(&charqueue->lock);
+       for (;;) {
+               if (n <= 0)
+                       break;  /* no more buffer space */
+               c = charqueue_dequeue_1(charqueue);
+               if (c < 0)
+                       break;  /* no more input */
+               *buf = (unsigned char)(c);
+               buf++;
+               n--;
+               counter++;
+       }
+       rc = counter;
+       spin_unlock(&charqueue->lock);
+       return rc;
+}
+EXPORT_SYMBOL_GPL(visor_charqueue_dequeue_n);
+
+void visor_charqueue_destroy(struct charqueue *charqueue)
+{
+       if (charqueue == NULL)
+               return;
+       kfree(charqueue);
+}
+EXPORT_SYMBOL_GPL(visor_charqueue_destroy);