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
  29 struct 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  */
  51 struct 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         uint    (*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  */
  95 struct 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  */
 116 int 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  */
 127 void posix_clock_unregister(struct posix_clock *clk);
 128
 129 #endif