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