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
29struct 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 * @timer_create:   Create a new timer
46 * @timer_delete:   Remove a previously created timer
47 * @timer_gettime:  Get remaining time and interval of a timer
48 * @timer_settime: Set a timer's initial expiration and interval
49 * @fasync:         Optional character device fasync method
50 * @mmap:           Optional character device mmap method
51 * @open:           Optional character device open method
52 * @release:        Optional character device release method
53 * @ioctl:          Optional character device ioctl method
54 * @read:           Optional character device read method
55 * @poll:           Optional character device poll method
56 */
57struct posix_clock_operations {
58	struct module *owner;
59
60	int  (*clock_adjtime)(struct posix_clock *pc, struct timex *tx);
61
62	int  (*clock_gettime)(struct posix_clock *pc, struct timespec *ts);
63
64	int  (*clock_getres) (struct posix_clock *pc, struct timespec *ts);
65
66	int  (*clock_settime)(struct posix_clock *pc,
67			      const struct timespec *ts);
68
69	int  (*timer_create) (struct posix_clock *pc, struct k_itimer *kit);
70
71	int  (*timer_delete) (struct posix_clock *pc, struct k_itimer *kit);
72
73	void (*timer_gettime)(struct posix_clock *pc,
74			      struct k_itimer *kit, struct itimerspec *tsp);
75
76	int  (*timer_settime)(struct posix_clock *pc,
77			      struct k_itimer *kit, int flags,
78			      struct itimerspec *tsp, struct itimerspec *old);
79	/*
80	 * Optional character device methods:
81	 */
82	int     (*fasync)  (struct posix_clock *pc,
83			    int fd, struct file *file, int on);
84
85	long    (*ioctl)   (struct posix_clock *pc,
86			    unsigned int cmd, unsigned long arg);
87
88	int     (*mmap)    (struct posix_clock *pc,
89			    struct vm_area_struct *vma);
90
91	int     (*open)    (struct posix_clock *pc, fmode_t f_mode);
92
93	uint    (*poll)    (struct posix_clock *pc,
94			    struct file *file, poll_table *wait);
95
96	int     (*release) (struct posix_clock *pc);
97
98	ssize_t (*read)    (struct posix_clock *pc,
99			    uint flags, char __user *buf, size_t cnt);
100};
101
102/**
103 * struct posix_clock - represents a dynamic posix clock
104 *
105 * @ops:     Functional interface to the clock
106 * @cdev:    Character device instance for this clock
107 * @kref:    Reference count.
108 * @rwsem:   Protects the 'zombie' field from concurrent access.
109 * @zombie:  If 'zombie' is true, then the hardware has disappeared.
110 * @release: A function to free the structure when the reference count reaches
111 *           zero. May be NULL if structure is statically allocated.
112 *
113 * Drivers should embed their struct posix_clock within a private
114 * structure, obtaining a reference to it during callbacks using
115 * container_of().
116 */
117struct posix_clock {
118	struct posix_clock_operations ops;
119	struct cdev cdev;
120	struct kref kref;
121	struct rw_semaphore rwsem;
122	bool zombie;
123	void (*release)(struct posix_clock *clk);
124};
125
126/**
127 * posix_clock_register() - register a new clock
128 * @clk:   Pointer to the clock. Caller must provide 'ops' and 'release'
129 * @devid: Allocated device id
130 *
131 * A clock driver calls this function to register itself with the
132 * clock device subsystem. If 'clk' points to dynamically allocated
133 * memory, then the caller must provide a 'release' function to free
134 * that memory.
135 *
136 * Returns zero on success, non-zero otherwise.
137 */
138int posix_clock_register(struct posix_clock *clk, dev_t devid);
139
140/**
141 * posix_clock_unregister() - unregister a clock
142 * @clk: Clock instance previously registered via posix_clock_register()
143 *
144 * A clock driver calls this function to remove itself from the clock
145 * device subsystem. The posix_clock itself will remain (in an
146 * inactive state) until its reference count drops to zero, at which
147 * point it will be deallocated with its 'release' method.
148 */
149void posix_clock_unregister(struct posix_clock *clk);
150
151#endif
152