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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
28struct posix_clock;
29
30/**
31 * struct posix_clock_operations - functional interface to the clock
32 *
33 * Every posix clock is represented by a character device. Drivers may
34 * optionally offer extended capabilities by implementing the
35 * character device methods. The character device file operations are
36 * first handled by the clock device layer, then passed on to the
37 * driver by calling these functions.
38 *
39 * @owner: The clock driver should set to THIS_MODULE
40 * @clock_adjtime: Adjust the clock
41 * @clock_gettime: Read the current time
42 * @clock_getres: Get the clock resolution
43 * @clock_settime: Set the current time value
44 * @timer_create: Create a new timer
45 * @timer_delete: Remove a previously created timer
46 * @timer_gettime: Get remaining time and interval of a timer
47 * @timer_setttime: Set a timer's initial expiration and interval
48 * @fasync: Optional character device fasync method
49 * @mmap: Optional character device mmap method
50 * @open: Optional character device open method
51 * @release: Optional character device release method
52 * @ioctl: Optional character device ioctl method
53 * @read: Optional character device read method
54 * @poll: Optional character device poll method
55 */
56struct posix_clock_operations {
57 struct module *owner;
58
59 int (*clock_adjtime)(struct posix_clock *pc, struct timex *tx);
60
61 int (*clock_gettime)(struct posix_clock *pc, struct timespec *ts);
62
63 int (*clock_getres) (struct posix_clock *pc, struct timespec *ts);
64
65 int (*clock_settime)(struct posix_clock *pc,
66 const struct timespec *ts);
67
68 int (*timer_create) (struct posix_clock *pc, struct k_itimer *kit);
69
70 int (*timer_delete) (struct posix_clock *pc, struct k_itimer *kit);
71
72 void (*timer_gettime)(struct posix_clock *pc,
73 struct k_itimer *kit, struct itimerspec *tsp);
74
75 int (*timer_settime)(struct posix_clock *pc,
76 struct k_itimer *kit, int flags,
77 struct itimerspec *tsp, struct itimerspec *old);
78 /*
79 * Optional character device methods:
80 */
81 int (*fasync) (struct posix_clock *pc,
82 int fd, struct file *file, int on);
83
84 long (*ioctl) (struct posix_clock *pc,
85 unsigned int cmd, unsigned long arg);
86
87 int (*mmap) (struct posix_clock *pc,
88 struct vm_area_struct *vma);
89
90 int (*open) (struct posix_clock *pc, fmode_t f_mode);
91
92 uint (*poll) (struct posix_clock *pc,
93 struct file *file, poll_table *wait);
94
95 int (*release) (struct posix_clock *pc);
96
97 ssize_t (*read) (struct posix_clock *pc,
98 uint flags, char __user *buf, size_t cnt);
99};
100
101/**
102 * struct posix_clock - represents a dynamic posix clock
103 *
104 * @ops: Functional interface to the clock
105 * @cdev: Character device instance for this clock
106 * @kref: Reference count.
107 * @mutex: Protects the 'zombie' field from concurrent access.
108 * @zombie: If 'zombie' is true, then the hardware has disappeared.
109 * @release: A function to free the structure when the reference count reaches
110 * zero. May be NULL if structure is statically allocated.
111 *
112 * Drivers should embed their struct posix_clock within a private
113 * structure, obtaining a reference to it during callbacks using
114 * container_of().
115 */
116struct posix_clock {
117 struct posix_clock_operations ops;
118 struct cdev cdev;
119 struct kref kref;
120 struct mutex mutex;
121 bool zombie;
122 void (*release)(struct posix_clock *clk);
123};
124
125/**
126 * posix_clock_register() - register a new clock
127 * @clk: Pointer to the clock. Caller must provide 'ops' and 'release'
128 * @devid: Allocated device id
129 *
130 * A clock driver calls this function to register itself with the
131 * clock device subsystem. If 'clk' points to dynamically allocated
132 * memory, then the caller must provide a 'release' function to free
133 * that memory.
134 *
135 * Returns zero on success, non-zero otherwise.
136 */
137int posix_clock_register(struct posix_clock *clk, dev_t devid);
138
139/**
140 * posix_clock_unregister() - unregister a clock
141 * @clk: Clock instance previously registered via posix_clock_register()
142 *
143 * A clock driver calls this function to remove itself from the clock
144 * device subsystem. The posix_clock itself will remain (in an
145 * inactive state) until its reference count drops to zero, at which
146 * point it will be deallocated with its 'release' method.
147 */
148void posix_clock_unregister(struct posix_clock *clk);
149
150#endif