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