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

   1/* SPDX-License-Identifier: GPL-2.0-or-later */
   2/*
   3 * posix-clock.h - support for dynamic clock devices
   4 *
   5 * Copyright (C) 2010 OMICRON electronics GmbH
   6 */
   7#ifndef _LINUX_POSIX_CLOCK_H_
   8#define _LINUX_POSIX_CLOCK_H_
   9
  10#include <linux/cdev.h>
  11#include <linux/fs.h>
  12#include <linux/poll.h>
  13#include <linux/posix-timers.h>
  14#include <linux/rwsem.h>
  15
  16struct posix_clock;
  17
  18/**
  19 * struct posix_clock_operations - functional interface to the clock
  20 *
  21 * Every posix clock is represented by a character device. Drivers may
  22 * optionally offer extended capabilities by implementing the
  23 * character device methods. The character device file operations are
  24 * first handled by the clock device layer, then passed on to the
  25 * driver by calling these functions.
  26 *
  27 * @owner:          The clock driver should set to THIS_MODULE
  28 * @clock_adjtime:  Adjust the clock
  29 * @clock_gettime:  Read the current time
  30 * @clock_getres:   Get the clock resolution
  31 * @clock_settime:  Set the current time value
  32 * @open:           Optional character device open method
  33 * @release:        Optional character device release method
  34 * @ioctl:          Optional character device ioctl method
  35 * @read:           Optional character device read method
  36 * @poll:           Optional character device poll method
  37 */
  38struct posix_clock_operations {
  39        struct module *owner;
  40
  41        int  (*clock_adjtime)(struct posix_clock *pc, struct __kernel_timex *tx);
  42
  43        int  (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts);
  44
  45        int  (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts);
  46
  47        int  (*clock_settime)(struct posix_clock *pc,
  48                              const struct timespec64 *ts);
  49
  50        /*
  51         * Optional character device methods:
  52         */
  53        long    (*ioctl)   (struct posix_clock *pc,
  54                            unsigned int cmd, unsigned long arg);
  55
  56        int     (*open)    (struct posix_clock *pc, fmode_t f_mode);
  57
  58        __poll_t (*poll)   (struct posix_clock *pc,
  59                            struct file *file, poll_table *wait);
  60
  61        int     (*release) (struct posix_clock *pc);
  62
  63        ssize_t (*read)    (struct posix_clock *pc,
  64                            uint flags, char __user *buf, size_t cnt);
  65};
  66
  67/**
  68 * struct posix_clock - represents a dynamic posix clock
  69 *
  70 * @ops:     Functional interface to the clock
  71 * @cdev:    Character device instance for this clock
  72 * @kref:    Reference count.
  73 * @rwsem:   Protects the 'zombie' field from concurrent access.
  74 * @zombie:  If 'zombie' is true, then the hardware has disappeared.
  75 * @release: A function to free the structure when the reference count reaches
  76 *           zero. May be NULL if structure is statically allocated.
  77 *
  78 * Drivers should embed their struct posix_clock within a private
  79 * structure, obtaining a reference to it during callbacks using
  80 * container_of().
  81 */
  82struct posix_clock {
  83        struct posix_clock_operations ops;
  84        struct cdev cdev;
  85        struct kref kref;
  86        struct rw_semaphore rwsem;
  87        bool zombie;
  88        void (*release)(struct posix_clock *clk);
  89};
  90
  91/**
  92 * posix_clock_register() - register a new clock
  93 * @clk:   Pointer to the clock. Caller must provide 'ops' and 'release'
  94 * @devid: Allocated device id
  95 *
  96 * A clock driver calls this function to register itself with the
  97 * clock device subsystem. If 'clk' points to dynamically allocated
  98 * memory, then the caller must provide a 'release' function to free
  99 * that memory.
 100 *
 101 * Returns zero on success, non-zero otherwise.
 102 */
 103int posix_clock_register(struct posix_clock *clk, dev_t devid);
 104
 105/**
 106 * posix_clock_unregister() - unregister a clock
 107 * @clk: Clock instance previously registered via posix_clock_register()
 108 *
 109 * A clock driver calls this function to remove itself from the clock
 110 * device subsystem. The posix_clock itself will remain (in an
 111 * inactive state) until its reference count drops to zero, at which
 112 * point it will be deallocated with its 'release' method.
 113 */
 114void posix_clock_unregister(struct posix_clock *clk);
 115
 116#endif
 117