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
  16 struct 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  */
  38 struct 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  * @dev:     Pointer to the clock's device.
  73  * @rwsem:   Protects the 'zombie' field from concurrent access.
  74  * @zombie:  If 'zombie' is true, then the hardware has disappeared.
  75  *
  76  * Drivers should embed their struct posix_clock within a private
  77  * structure, obtaining a reference to it during callbacks using
  78  * container_of().
  79  *
  80  * Drivers should supply an initialized but not exposed struct device
  81  * to posix_clock_register(). It is used to manage lifetime of the
  82  * driver's private structure. It's 'release' field should be set to
  83  * a release function for this private structure.
  84  */
  85 struct posix_clock {
  86         struct posix_clock_operations ops;
  87         struct cdev cdev;
  88         struct device *dev;
  89         struct rw_semaphore rwsem;
  90         bool zombie;
  91 };
  92
  93 /**
  94  * posix_clock_register() - register a new clock
  95  * @clk:   Pointer to the clock. Caller must provide 'ops' field
  96  * @dev:   Pointer to the initialized device. Caller must provide
  97  *         'release' field
  98  *
  99  * A clock driver calls this function to register itself with the
 100  * clock device subsystem. If 'clk' points to dynamically allocated
 101  * memory, then the caller must provide a 'release' function to free
 102  * that memory.
 103  *
 104  * Returns zero on success, non-zero otherwise.
 105  */
 106 int posix_clock_register(struct posix_clock *clk, struct device *dev);
 107
 108 /**
 109  * posix_clock_unregister() - unregister a clock
 110  * @clk: Clock instance previously registered via posix_clock_register()
 111  *
 112  * A clock driver calls this function to remove itself from the clock
 113  * device subsystem. The posix_clock itself will remain (in an
 114  * inactive state) until its reference count drops to zero, at which
 115  * point it will be deallocated with its 'release' method.
 116  */
 117 void posix_clock_unregister(struct posix_clock *clk);
 118
 119 #endif