include/linux/relay.h

1 /* SPDX-License-Identifier: GPL-2.0 */
5  * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
6  * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
32  * Per-cpu relay channel buffer
36 	void *start;			/* start of channel buffer */
37 	void *data;			/* start of current sub-buffer */
38 	size_t offset;			/* current offset into sub-buffer */
39 	size_t subbufs_produced;	/* count of sub-buffers produced */
40 	size_t subbufs_consumed;	/* count of sub-buffers consumed */
41 	struct rchan *chan;		/* associated channel */
44 	struct dentry *dentry;		/* channel file dentry */
45 	struct kref kref;		/* channel buffer refcount */
49 	size_t *padding;		/* padding counts per sub-buffer */
57  * Relay channel data structure
62 	size_t subbuf_size;		/* sub-buffer size */
63 	size_t n_subbufs;		/* number of sub-buffers per buffer */
66 	struct kref kref;		/* channel refcount */
67 	void *private_data;		/* for user-defined data */
69 	struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
71 	struct list_head list;		/* for channel list */
78  * Relay channel client callbacks
83 	 * subbuf_start - called on buffer-switch to a new sub-buffer
84 	 * @buf: the channel buffer containing the new sub-buffer
85 	 * @subbuf: the start of the new sub-buffer
86 	 * @prev_subbuf: the start of the previous sub-buffer
87 	 * @prev_padding: unused space at the end of previous sub-buffer
95 	 *       created, so that the first sub-buffer can be initialized
99 	 *       sub-buffer by calling subbuf_start_reserve() in this callback.
107 	 * create_buf_file - create file to represent a relay channel buffer
111 	 * @buf: the channel buffer
112 	 * @is_global: outparam - set non-zero if the buffer should be global
114 	 * Called during relay_open(), once for each per-cpu buffer,
116 	 * represent the corresponding channel buffer.  If the file is
123 	 * Setting the is_global outparam to a non-zero value will
125 	 * than the default set of per-cpu buffers.
138 	 * remove_buf_file - remove file representing a relay channel buffer
141 	 * Called during relay_close(), once for each per-cpu buffer,
143 	 * channel buffer.
177  *	relay_write - write data into the channel
178  *	@chan: relay channel
182  *	Writes data into the current cpu's channel buffer.
197 	buf = *this_cpu_ptr(chan->buf);  in relay_write()
198 	if (unlikely(buf->offset + length > chan->subbuf_size))  in relay_write()
200 	memcpy(buf->data + buf->offset, data, length);  in relay_write()
201 	buf->offset += length;  in relay_write()
206  *	__relay_write - write data into the channel
207  *	@chan: relay channel
211  *	Writes data into the current cpu's channel buffer.
223 	buf = *get_cpu_ptr(chan->buf);  in __relay_write()
224 	if (unlikely(buf->offset + length > buf->chan->subbuf_size))  in __relay_write()
226 	memcpy(buf->data + buf->offset, data, length);  in __relay_write()
227 	buf->offset += length;  in __relay_write()
228 	put_cpu_ptr(chan->buf);  in __relay_write()
232  *	relay_reserve - reserve slot in channel buffer
233  *	@chan: relay channel
238  *	Reserves a slot in the current cpu's channel buffer.
239  *	Does not protect the buffer at all - caller must provide
245 	struct rchan_buf *buf = *get_cpu_ptr(chan->buf);  in relay_reserve()
247 	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {  in relay_reserve()
252 	reserved = buf->data + buf->offset;  in relay_reserve()
253 	buf->offset += length;  in relay_reserve()
256 	put_cpu_ptr(chan->buf);  in relay_reserve()
261  *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer
262  *	@buf: relay channel buffer
266  *	a sub-buffer in the subbuf_start() callback.
271 	BUG_ON(length >= buf->chan->subbuf_size - 1);  in subbuf_start_reserve()
272 	buf->offset = length;  in subbuf_start_reserve()