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 struct posix_clock_context;
  18
  19 /**
  20  * struct posix_clock_operations - functional interface to the clock
  21  *
  22  * Every posix clock is represented by a character device. Drivers may
  23  * optionally offer extended capabilities by implementing the
  24  * character device methods. The character device file operations are
  25  * first handled by the clock device layer, then passed on to the
  26  * driver by calling these functions.
  27  *
  28  * @owner:          The clock driver should set to THIS_MODULE
  29  * @clock_adjtime:  Adjust the clock
  30  * @clock_gettime:  Read the current time
  31  * @clock_getres:   Get the clock resolution
  32  * @clock_settime:  Set the current time value
  33  * @open:           Optional character device open method
  34  * @release:        Optional character device release method
  35  * @ioctl:          Optional character device ioctl method
  36  * @read:           Optional character device read method
  37  * @poll:           Optional character device poll method
  38  */
  39 struct posix_clock_operations {
  40         struct module *owner;
  41
  42         int  (*clock_adjtime)(struct posix_clock *pc, struct __kernel_timex *tx);
  43
  44         int  (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts);
  45
  46         int  (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts);
  47
  48         int  (*clock_settime)(struct posix_clock *pc,
  49                               const struct timespec64 *ts);
  50
  51         /*
  52          * Optional character device methods:
  53          */
  54         long (*ioctl)(struct posix_clock_context *pccontext, unsigned int cmd,
  55                       unsigned long arg);
  56
  57         int (*open)(struct posix_clock_context *pccontext, fmode_t f_mode);
  58
  59         __poll_t (*poll)(struct posix_clock_context *pccontext, struct file *file,
  60                          poll_table *wait);
  61
  62         int (*release)(struct posix_clock_context *pccontext);
  63
  64         ssize_t (*read)(struct posix_clock_context *pccontext, uint flags,
  65                         char __user *buf, size_t cnt);
  66 };
  67
  68 /**
  69  * struct posix_clock - represents a dynamic posix clock
  70  *
  71  * @ops:     Functional interface to the clock
  72  * @cdev:    Character device instance for this clock
  73  * @dev:     Pointer to the clock's device.
  74  * @rwsem:   Protects the 'zombie' field from concurrent access.
  75  * @zombie:  If 'zombie' is true, then the hardware has disappeared.
  76  *
  77  * Drivers should embed their struct posix_clock within a private
  78  * structure, obtaining a reference to it during callbacks using
  79  * container_of().
  80  *
  81  * Drivers should supply an initialized but not exposed struct device
  82  * to posix_clock_register(). It is used to manage lifetime of the
  83  * driver's private structure. It's 'release' field should be set to
  84  * a release function for this private structure.
  85  */
  86 struct posix_clock {
  87         struct posix_clock_operations ops;
  88         struct cdev cdev;
  89         struct device *dev;
  90         struct rw_semaphore rwsem;
  91         bool zombie;
  92 };
  93
  94 /**
  95  * struct posix_clock_context - represents clock file operations context
  96  *
  97  * @clk:              Pointer to the clock
  98  * @private_clkdata:  Pointer to user data
  99  *
 100  * Drivers should use struct posix_clock_context during specific character
 101  * device file operation methods to access the posix clock.
 102  *
 103  * Drivers can store a private data structure during the open operation
 104  * if they have specific information that is required in other file
 105  * operations.
 106  */
 107 struct posix_clock_context {
 108         struct posix_clock *clk;
 109         void *private_clkdata;
 110 };
 111
 112 /**
 113  * posix_clock_register() - register a new clock
 114  * @clk:   Pointer to the clock. Caller must provide 'ops' field
 115  * @dev:   Pointer to the initialized device. Caller must provide
 116  *         'release' field
 117  *
 118  * A clock driver calls this function to register itself with the
 119  * clock device subsystem. If 'clk' points to dynamically allocated
 120  * memory, then the caller must provide a 'release' function to free
 121  * that memory.
 122  *
 123  * Returns zero on success, non-zero otherwise.
 124  */
 125 int posix_clock_register(struct posix_clock *clk, struct device *dev);
 126
 127 /**
 128  * posix_clock_unregister() - unregister a clock
 129  * @clk: Clock instance previously registered via posix_clock_register()
 130  *
 131  * A clock driver calls this function to remove itself from the clock
 132  * device subsystem. The posix_clock itself will remain (in an
 133  * inactive state) until its reference count drops to zero, at which
 134  * point it will be deallocated with its 'release' method.
 135  */
 136 void posix_clock_unregister(struct posix_clock *clk);
 137
 138 #endif