--- /dev/null
+/*
+ * posix-clock.h - support for dynamic clock devices
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ *
+ * 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. 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#ifndef _LINUX_POSIX_CLOCK_H_
+#define _LINUX_POSIX_CLOCK_H_
+
+#include <linux/cdev.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/posix-timers.h>
+#include <linux/rwsem.h>
+
+struct posix_clock;
+
+/**
+ * struct posix_clock_operations - functional interface to the clock
+ *
+ * Every posix clock is represented by a character device. Drivers may
+ * optionally offer extended capabilities by implementing the
+ * character device methods. The character device file operations are
+ * first handled by the clock device layer, then passed on to the
+ * driver by calling these functions.
+ *
+ * @owner: The clock driver should set to THIS_MODULE
+ * @clock_adjtime: Adjust the clock
+ * @clock_gettime: Read the current time
+ * @clock_getres: Get the clock resolution
+ * @clock_settime: Set the current time value
+ * @timer_create: Create a new timer
+ * @timer_delete: Remove a previously created timer
+ * @timer_gettime: Get remaining time and interval of a timer
+ * @timer_settime: Set a timer's initial expiration and interval
+ * @fasync: Optional character device fasync method
+ * @mmap: Optional character device mmap method
+ * @open: Optional character device open method
+ * @release: Optional character device release method
+ * @ioctl: Optional character device ioctl method
+ * @read: Optional character device read method
+ * @poll: Optional character device poll method
+ */
+struct posix_clock_operations {
+ struct module *owner;
+
+ int (*clock_adjtime)(struct posix_clock *pc, struct timex *tx);
+
+ int (*clock_gettime)(struct posix_clock *pc, struct timespec *ts);
+
+ int (*clock_getres) (struct posix_clock *pc, struct timespec *ts);
+
+ int (*clock_settime)(struct posix_clock *pc,
+ const struct timespec *ts);
+
+ int (*timer_create) (struct posix_clock *pc, struct k_itimer *kit);
+
+ int (*timer_delete) (struct posix_clock *pc, struct k_itimer *kit);
+
+ void (*timer_gettime)(struct posix_clock *pc,
+ struct k_itimer *kit, struct itimerspec *tsp);
+
+ int (*timer_settime)(struct posix_clock *pc,
+ struct k_itimer *kit, int flags,
+ struct itimerspec *tsp, struct itimerspec *old);
+ /*
+ * Optional character device methods:
+ */
+ int (*fasync) (struct posix_clock *pc,
+ int fd, struct file *file, int on);
+
+ long (*ioctl) (struct posix_clock *pc,
+ unsigned int cmd, unsigned long arg);
+
+ int (*mmap) (struct posix_clock *pc,
+ struct vm_area_struct *vma);
+
+ int (*open) (struct posix_clock *pc, fmode_t f_mode);
+
+ uint (*poll) (struct posix_clock *pc,
+ struct file *file, poll_table *wait);
+
+ int (*release) (struct posix_clock *pc);
+
+ ssize_t (*read) (struct posix_clock *pc,
+ uint flags, char __user *buf, size_t cnt);
+};
+
+/**
+ * struct posix_clock - represents a dynamic posix clock
+ *
+ * @ops: Functional interface to the clock
+ * @cdev: Character device instance for this clock
+ * @kref: Reference count.
+ * @rwsem: Protects the 'zombie' field from concurrent access.
+ * @zombie: If 'zombie' is true, then the hardware has disappeared.
+ * @release: A function to free the structure when the reference count reaches
+ * zero. May be NULL if structure is statically allocated.
+ *
+ * Drivers should embed their struct posix_clock within a private
+ * structure, obtaining a reference to it during callbacks using
+ * container_of().
+ */
+struct posix_clock {
+ struct posix_clock_operations ops;
+ struct cdev cdev;
+ struct kref kref;
+ struct rw_semaphore rwsem;
+ bool zombie;
+ void (*release)(struct posix_clock *clk);
+};
+
+/**
+ * posix_clock_register() - register a new clock
+ * @clk: Pointer to the clock. Caller must provide 'ops' and 'release'
+ * @devid: Allocated device id
+ *
+ * A clock driver calls this function to register itself with the
+ * clock device subsystem. If 'clk' points to dynamically allocated
+ * memory, then the caller must provide a 'release' function to free
+ * that memory.
+ *
+ * Returns zero on success, non-zero otherwise.
+ */
+int posix_clock_register(struct posix_clock *clk, dev_t devid);
+
+/**
+ * posix_clock_unregister() - unregister a clock
+ * @clk: Clock instance previously registered via posix_clock_register()
+ *
+ * A clock driver calls this function to remove itself from the clock
+ * device subsystem. The posix_clock itself will remain (in an
+ * inactive state) until its reference count drops to zero, at which
+ * point it will be deallocated with its 'release' method.
+ */
+void posix_clock_unregister(struct posix_clock *clk);
+
+#endif
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