LXR linux/include/linux/posix-clock.h

   1/*
   2 * posix-clock.h - support for dynamic clock devices
   3 *
   4 * Copyright (C) 2010 OMICRON electronics GmbH
   5 *
   6 *  This program is free software; you can redistribute it and/or modify
   7 *  it under the terms of the GNU General Public License as published by
   8 *  the Free Software Foundation; either version 2 of the License, or
   9 *  (at your option) any later version.
  10 *
  11 *  This program is distributed in the hope that it will be useful,
  12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 *  GNU General Public License for more details.
  15 *
  16 *  You should have received a copy of the GNU General Public License
  17 *  along with this program; if not, write to the Free Software
  18 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20#ifndef _LINUX_POSIX_CLOCK_H_
  21#define _LINUX_POSIX_CLOCK_H_
  22
  23#include <linux/cdev.h>
  24#include <linux/fs.h>
  25#include <linux/poll.h>
  26#include <linux/posix-timers.h>
  27#include <linux/rwsem.h>
  28
  29struct posix_clock;
  30
  31/**
  32 * struct posix_clock_operations - functional interface to the clock
  33 *
  34 * Every posix clock is represented by a character device. Drivers may
  35 * optionally offer extended capabilities by implementing the
  36 * character device methods. The character device file operations are
  37 * first handled by the clock device layer, then passed on to the
  38 * driver by calling these functions.
  39 *
  40 * @owner:          The clock driver should set to THIS_MODULE
  41 * @clock_adjtime:  Adjust the clock
  42 * @clock_gettime:  Read the current time
  43 * @clock_getres:   Get the clock resolution
  44 * @clock_settime:  Set the current time value
  45 * @open:           Optional character device open method
  46 * @release:        Optional character device release method
  47 * @ioctl:          Optional character device ioctl method
  48 * @read:           Optional character device read method
  49 * @poll:           Optional character device poll method
  50 */
  51struct posix_clock_operations {
  52        struct module *owner;
  53
  54        int  (*clock_adjtime)(struct posix_clock *pc, struct timex *tx);
  55
  56        int  (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts);
  57
  58        int  (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts);
  59
  60        int  (*clock_settime)(struct posix_clock *pc,
  61                              const struct timespec64 *ts);
  62
  63        /*
  64         * Optional character device methods:
  65         */
  66        long    (*ioctl)   (struct posix_clock *pc,
  67                            unsigned int cmd, unsigned long arg);
  68
  69        int     (*open)    (struct posix_clock *pc, fmode_t f_mode);
  70
  71        __poll_t (*poll)   (struct posix_clock *pc,
  72                            struct file *file, poll_table *wait);
  73
  74        int     (*release) (struct posix_clock *pc);
  75
  76        ssize_t (*read)    (struct posix_clock *pc,
  77                            uint flags, char __user *buf, size_t cnt);
  78};
  79
  80/**
  81 * struct posix_clock - represents a dynamic posix clock
  82 *
  83 * @ops:     Functional interface to the clock
  84 * @cdev:    Character device instance for this clock
  85 * @kref:    Reference count.
  86 * @rwsem:   Protects the 'zombie' field from concurrent access.
  87 * @zombie:  If 'zombie' is true, then the hardware has disappeared.
  88 * @release: A function to free the structure when the reference count reaches
  89 *           zero. May be NULL if structure is statically allocated.
  90 *
  91 * Drivers should embed their struct posix_clock within a private
  92 * structure, obtaining a reference to it during callbacks using
  93 * container_of().
  94 */
  95struct posix_clock {
  96        struct posix_clock_operations ops;
  97        struct cdev cdev;
  98        struct kref kref;
  99        struct rw_semaphore rwsem;
 100        bool zombie;
 101        void (*release)(struct posix_clock *clk);
 102};
 103
 104/**
 105 * posix_clock_register() - register a new clock
 106 * @clk:   Pointer to the clock. Caller must provide 'ops' and 'release'
 107 * @devid: Allocated device id
 108 *
 109 * A clock driver calls this function to register itself with the
 110 * clock device subsystem. If 'clk' points to dynamically allocated
 111 * memory, then the caller must provide a 'release' function to free
 112 * that memory.
 113 *
 114 * Returns zero on success, non-zero otherwise.
 115 */
 116int posix_clock_register(struct posix_clock *clk, dev_t devid);
 117
 118/**
 119 * posix_clock_unregister() - unregister a clock
 120 * @clk: Clock instance previously registered via posix_clock_register()
 121 *
 122 * A clock driver calls this function to remove itself from the clock
 123 * device subsystem. The posix_clock itself will remain (in an
 124 * inactive state) until its reference count drops to zero, at which
 125 * point it will be deallocated with its 'release' method.
 126 */
 127void posix_clock_unregister(struct posix_clock *clk);
 128
 129#endif
 130