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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 #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 * @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 */
57 struct 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 */
117 struct 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 */
138 int 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 */
149 void posix_clock_unregister(struct posix_clock *clk);
150
151 #endif