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
16struct posix_clock;
17struct posix_clock_context;
18
19/**
20 * struct posix_clock_operations - functional interface to the clock
21 *
22 * Every posix clock is represented by a character device. Drivers may
23 * optionally offer extended capabilities by implementing the
24 * character device methods. The character device file operations are
25 * first handled by the clock device layer, then passed on to the
26 * driver by calling these functions.
27 *
28 * @owner:          The clock driver should set to THIS_MODULE
29 * @clock_adjtime:  Adjust the clock
30 * @clock_gettime:  Read the current time
31 * @clock_getres:   Get the clock resolution
32 * @clock_settime:  Set the current time value
33 * @open:           Optional character device open method
34 * @release:        Optional character device release method
35 * @ioctl:          Optional character device ioctl method
36 * @read:           Optional character device read method
37 * @poll:           Optional character device poll method
38 */
39struct posix_clock_operations {
40	struct module *owner;
41
42	int  (*clock_adjtime)(struct posix_clock *pc, struct __kernel_timex *tx);
43
44	int  (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts);
45
46	int  (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts);
47
48	int  (*clock_settime)(struct posix_clock *pc,
49			      const struct timespec64 *ts);
50
51	/*
52	 * Optional character device methods:
53	 */
54	long (*ioctl)(struct posix_clock_context *pccontext, unsigned int cmd,
55		      unsigned long arg);
56
57	int (*open)(struct posix_clock_context *pccontext, fmode_t f_mode);
58
59	__poll_t (*poll)(struct posix_clock_context *pccontext, struct file *file,
60			 poll_table *wait);
61
62	int (*release)(struct posix_clock_context *pccontext);
63
64	ssize_t (*read)(struct posix_clock_context *pccontext, uint flags,
65			char __user *buf, size_t cnt);
66};
67
68/**
69 * struct posix_clock - represents a dynamic posix clock
70 *
71 * @ops:     Functional interface to the clock
72 * @cdev:    Character device instance for this clock
73 * @dev:     Pointer to the clock's device.
74 * @rwsem:   Protects the 'zombie' field from concurrent access.
75 * @zombie:  If 'zombie' is true, then the hardware has disappeared.
76 *
77 * Drivers should embed their struct posix_clock within a private
78 * structure, obtaining a reference to it during callbacks using
79 * container_of().
80 *
81 * Drivers should supply an initialized but not exposed struct device
82 * to posix_clock_register(). It is used to manage lifetime of the
83 * driver's private structure. It's 'release' field should be set to
84 * a release function for this private structure.
85 */
86struct posix_clock {
87	struct posix_clock_operations ops;
88	struct cdev cdev;
89	struct device *dev;
90	struct rw_semaphore rwsem;
91	bool zombie;
92};
93
94/**
95 * struct posix_clock_context - represents clock file operations context
96 *
97 * @clk:              Pointer to the clock
98 * @private_clkdata:  Pointer to user data
99 *
100 * Drivers should use struct posix_clock_context during specific character
101 * device file operation methods to access the posix clock.
102 *
103 * Drivers can store a private data structure during the open operation
104 * if they have specific information that is required in other file
105 * operations.
106 */
107struct posix_clock_context {
108	struct posix_clock *clk;
109	void *private_clkdata;
110};
111
112/**
113 * posix_clock_register() - register a new clock
114 * @clk:   Pointer to the clock. Caller must provide 'ops' field
115 * @dev:   Pointer to the initialized device. Caller must provide
116 *         'release' field
117 *
118 * A clock driver calls this function to register itself with the
119 * clock device subsystem. If 'clk' points to dynamically allocated
120 * memory, then the caller must provide a 'release' function to free
121 * that memory.
122 *
123 * Returns zero on success, non-zero otherwise.
124 */
125int posix_clock_register(struct posix_clock *clk, struct device *dev);
126
127/**
128 * posix_clock_unregister() - unregister a clock
129 * @clk: Clock instance previously registered via posix_clock_register()
130 *
131 * A clock driver calls this function to remove itself from the clock
132 * device subsystem. The posix_clock itself will remain (in an
133 * inactive state) until its reference count drops to zero, at which
134 * point it will be deallocated with its 'release' method.
135 */
136void posix_clock_unregister(struct posix_clock *clk);
137
138#endif
139