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Diffstat (limited to 'include/linux/posix-clock.h')
| -rw-r--r-- | include/linux/posix-clock.h | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/include/linux/posix-clock.h b/include/linux/posix-clock.h new file mode 100644 index 000000000..468328b1e --- /dev/null +++ b/include/linux/posix-clock.h @@ -0,0 +1,119 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * posix-clock.h - support for dynamic clock devices + * + * Copyright (C) 2010 OMICRON electronics GmbH + */ +#ifndef _LINUX_POSIX_CLOCK_H_ +#define _LINUX_POSIX_CLOCK_H_ + +#include <linux/cdev.h> +#include <linux/fs.h> +#include <linux/poll.h> +#include <linux/posix-timers.h> +#include <linux/rwsem.h> + +struct posix_clock; + +/** + * struct posix_clock_operations - functional interface to the clock + * + * Every posix clock is represented by a character device. Drivers may + * optionally offer extended capabilities by implementing the + * character device methods. The character device file operations are + * first handled by the clock device layer, then passed on to the + * driver by calling these functions. + * + * @owner: The clock driver should set to THIS_MODULE + * @clock_adjtime: Adjust the clock + * @clock_gettime: Read the current time + * @clock_getres: Get the clock resolution + * @clock_settime: Set the current time value + * @open: Optional character device open method + * @release: Optional character device release method + * @ioctl: Optional character device ioctl method + * @read: Optional character device read method + * @poll: Optional character device poll method + */ +struct posix_clock_operations { + struct module *owner; + + int (*clock_adjtime)(struct posix_clock *pc, struct __kernel_timex *tx); + + int (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts); + + int (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts); + + int (*clock_settime)(struct posix_clock *pc, + const struct timespec64 *ts); + + /* + * Optional character device methods: + */ + long (*ioctl) (struct posix_clock *pc, + unsigned int cmd, unsigned long arg); + + int (*open) (struct posix_clock *pc, fmode_t f_mode); + + __poll_t (*poll) (struct posix_clock *pc, + struct file *file, poll_table *wait); + + int (*release) (struct posix_clock *pc); + + ssize_t (*read) (struct posix_clock *pc, + uint flags, char __user *buf, size_t cnt); +}; + +/** + * struct posix_clock - represents a dynamic posix clock + * + * @ops: Functional interface to the clock + * @cdev: Character device instance for this clock + * @dev: Pointer to the clock's device. + * @rwsem: Protects the 'zombie' field from concurrent access. + * @zombie: If 'zombie' is true, then the hardware has disappeared. + * + * Drivers should embed their struct posix_clock within a private + * structure, obtaining a reference to it during callbacks using + * container_of(). + * + * Drivers should supply an initialized but not exposed struct device + * to posix_clock_register(). It is used to manage lifetime of the + * driver's private structure. It's 'release' field should be set to + * a release function for this private structure. + */ +struct posix_clock { + struct posix_clock_operations ops; + struct cdev cdev; + struct device *dev; + struct rw_semaphore rwsem; + bool zombie; +}; + +/** + * posix_clock_register() - register a new clock + * @clk: Pointer to the clock. Caller must provide 'ops' field + * @dev: Pointer to the initialized device. Caller must provide + * 'release' field + * + * A clock driver calls this function to register itself with the + * clock device subsystem. If 'clk' points to dynamically allocated + * memory, then the caller must provide a 'release' function to free + * that memory. + * + * Returns zero on success, non-zero otherwise. + */ +int posix_clock_register(struct posix_clock *clk, struct device *dev); + +/** + * posix_clock_unregister() - unregister a clock + * @clk: Clock instance previously registered via posix_clock_register() + * + * A clock driver calls this function to remove itself from the clock + * device subsystem. The posix_clock itself will remain (in an + * inactive state) until its reference count drops to zero, at which + * point it will be deallocated with its 'release' method. + */ +void posix_clock_unregister(struct posix_clock *clk); + +#endif |