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 152