linux/include/linux/relay.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * linux/include/linux/relay.h
 *
 * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp
 * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected])
 *
 * CONFIG_RELAY definitions and declarations
 */

#ifndef _LINUX_RELAY_H
#define _LINUX_RELAY_H

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/list.h>
#include <linux/irq_work.h>
#include <linux/bug.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.h>
#include <linux/percpu.h>

/*
 * Tracks changes to rchan/rchan_buf structs
 */
#define RELAYFS_CHANNEL_VERSION …

/*
 * Per-cpu relay channel buffer
 */
struct rchan_buf
{ … } ____cacheline_aligned;

/*
 * Relay channel data structure
 */
struct rchan
{ … };

/*
 * Relay channel client callbacks
 */
struct rchan_callbacks
{ … };

/*
 * CONFIG_RELAY kernel API, kernel/relay.c
 */

struct rchan *relay_open(const char *base_filename,
			 struct dentry *parent,
			 size_t subbuf_size,
			 size_t n_subbufs,
			 const struct rchan_callbacks *cb,
			 void *private_data);
extern int relay_late_setup_files(struct rchan *chan,
				  const char *base_filename,
				  struct dentry *parent);
extern void relay_close(struct rchan *chan);
extern void relay_flush(struct rchan *chan);
extern void relay_subbufs_consumed(struct rchan *chan,
				   unsigned int cpu,
				   size_t consumed);
extern void relay_reset(struct rchan *chan);
extern int relay_buf_full(struct rchan_buf *buf);

extern size_t relay_switch_subbuf(struct rchan_buf *buf,
				  size_t length);

/**
 *	relay_write - write data into the channel
 *	@chan: relay channel
 *	@data: data to be written
 *	@length: number of bytes to write
 *
 *	Writes data into the current cpu's channel buffer.
 *
 *	Protects the buffer by disabling interrupts.  Use this
 *	if you might be logging from interrupt context.  Try
 *	__relay_write() if you know you	won't be logging from
 *	interrupt context.
 */
static inline void relay_write(struct rchan *chan,
			       const void *data,
			       size_t length)
{ … }

/**
 *	__relay_write - write data into the channel
 *	@chan: relay channel
 *	@data: data to be written
 *	@length: number of bytes to write
 *
 *	Writes data into the current cpu's channel buffer.
 *
 *	Protects the buffer by disabling preemption.  Use
 *	relay_write() if you might be logging from interrupt
 *	context.
 */
static inline void __relay_write(struct rchan *chan,
				 const void *data,
				 size_t length)
{ … }

/**
 *	relay_reserve - reserve slot in channel buffer
 *	@chan: relay channel
 *	@length: number of bytes to reserve
 *
 *	Returns pointer to reserved slot, NULL if full.
 *
 *	Reserves a slot in the current cpu's channel buffer.
 *	Does not protect the buffer at all - caller must provide
 *	appropriate synchronization.
 */
static inline void *relay_reserve(struct rchan *chan, size_t length)
{ … }

/**
 *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer
 *	@buf: relay channel buffer
 *	@length: number of bytes to reserve
 *
 *	Helper function used to reserve bytes at the beginning of
 *	a sub-buffer in the subbuf_start() callback.
 */
static inline void subbuf_start_reserve(struct rchan_buf *buf,
					size_t length)
{ … }

/*
 * exported relay file operations, kernel/relay.c
 */
extern const struct file_operations relay_file_operations;

#ifdef CONFIG_RELAY
int relay_prepare_cpu(unsigned int cpu);
#else
#define relay_prepare_cpu …
#endif

#endif /* _LINUX_RELAY_H */