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 * @open: Optional character device open method 46 * @release: Optional character device release method 47 * @ioctl: Optional character device ioctl method 48 * @read: Optional character device read method 49 * @poll: Optional character device poll method 50 */ 51 struct posix_clock_operations { 52 struct module *owner; 53 54 int (*clock_adjtime)(struct posix_clock *pc, struct __kernel_timex *tx); 55 56 int (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts); 57 58 int (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts); 59 60 int (*clock_settime)(struct posix_clock *pc, 61 const struct timespec64 *ts); 62 63 /* 64 * Optional character device methods: 65 */ 66 long (*ioctl) (struct posix_clock *pc, 67 unsigned int cmd, unsigned long arg); 68 69 int (*open) (struct posix_clock *pc, fmode_t f_mode); 70 71 __poll_t (*poll) (struct posix_clock *pc, 72 struct file *file, poll_table *wait); 73 74 int (*release) (struct posix_clock *pc); 75 76 ssize_t (*read) (struct posix_clock *pc, 77 uint flags, char __user *buf, size_t cnt); 78 }; 79 80 /** 81 * struct posix_clock - represents a dynamic posix clock 82 * 83 * @ops: Functional interface to the clock 84 * @cdev: Character device instance for this clock 85 * @kref: Reference count. 86 * @rwsem: Protects the 'zombie' field from concurrent access. 87 * @zombie: If 'zombie' is true, then the hardware has disappeared. 88 * @release: A function to free the structure when the reference count reaches 89 * zero. May be NULL if structure is statically allocated. 90 * 91 * Drivers should embed their struct posix_clock within a private 92 * structure, obtaining a reference to it during callbacks using 93 * container_of(). 94 */ 95 struct posix_clock { 96 struct posix_clock_operations ops; 97 struct cdev cdev; 98 struct kref kref; 99 struct rw_semaphore rwsem; 100 bool zombie; 101 void (*release)(struct posix_clock *clk); 102 }; 103 104 /** 105 * posix_clock_register() - register a new clock 106 * @clk: Pointer to the clock. Caller must provide 'ops' and 'release' 107 * @devid: Allocated device id 108 * 109 * A clock driver calls this function to register itself with the 110 * clock device subsystem. If 'clk' points to dynamically allocated 111 * memory, then the caller must provide a 'release' function to free 112 * that memory. 113 * 114 * Returns zero on success, non-zero otherwise. 115 */ 116 int posix_clock_register(struct posix_clock *clk, dev_t devid); 117 118 /** 119 * posix_clock_unregister() - unregister a clock 120 * @clk: Clock instance previously registered via posix_clock_register() 121 * 122 * A clock driver calls this function to remove itself from the clock 123 * device subsystem. The posix_clock itself will remain (in an 124 * inactive state) until its reference count drops to zero, at which 125 * point it will be deallocated with its 'release' method. 126 */ 127 void posix_clock_unregister(struct posix_clock *clk); 128 129 #endif 130