1/*
2 *
3 * dvb_ringbuffer.c: ring buffer implementation for the dvb driver
4 *
5 * Copyright (C) 2003 Oliver Endriss
6 * Copyright (C) 2004 Andrew de Quincey
7 *
8 * based on code originally found in av7110.c & dvb_ci.c:
9 * Copyright (C) 1999-2003 Ralph  Metzler
10 *                       & Marcus Metzler for convergence integrated media GmbH
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU Lesser General Public License
14 * as published by the Free Software Foundation; either version 2.1
15 * of the License, or (at your option) any later version.
16 *
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
20 * GNU Lesser General Public License for more details.
21 */
22
23
24
25#include <linux/errno.h>
26#include <linux/kernel.h>
27#include <linux/module.h>
28#include <linux/sched.h>
29#include <linux/string.h>
30#include <linux/uaccess.h>
31
32#include <media/dvb_ringbuffer.h>
33
34#define PKT_READY 0
35#define PKT_DISPOSED 1
36
37
38void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len)
39{
40	rbuf->pread=rbuf->pwrite=0;
41	rbuf->data=data;
42	rbuf->size=len;
43	rbuf->error=0;
44
45	init_waitqueue_head(&rbuf->queue);
46
47	spin_lock_init(&(rbuf->lock));
48}
49
50
51
52int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf)
53{
54	/* smp_load_acquire() to load write pointer on reader side
55	 * this pairs with smp_store_release() in dvb_ringbuffer_write(),
56	 * dvb_ringbuffer_write_user(), or dvb_ringbuffer_reset()
57	 *
58	 * for memory barriers also see Documentation/core-api/circular-buffers.rst
59	 */
60	return (rbuf->pread == smp_load_acquire(&rbuf->pwrite));
61}
62
63
64
65ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf)
66{
67	ssize_t free;
68
69	/* READ_ONCE() to load read pointer on writer side
70	 * this pairs with smp_store_release() in dvb_ringbuffer_read(),
71	 * dvb_ringbuffer_read_user(), dvb_ringbuffer_flush(),
72	 * or dvb_ringbuffer_reset()
73	 */
74	free = READ_ONCE(rbuf->pread) - rbuf->pwrite;
75	if (free <= 0)
76		free += rbuf->size;
77	return free-1;
78}
79
80
81
82ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf)
83{
84	ssize_t avail;
85
86	/* smp_load_acquire() to load write pointer on reader side
87	 * this pairs with smp_store_release() in dvb_ringbuffer_write(),
88	 * dvb_ringbuffer_write_user(), or dvb_ringbuffer_reset()
89	 */
90	avail = smp_load_acquire(&rbuf->pwrite) - rbuf->pread;
91	if (avail < 0)
92		avail += rbuf->size;
93	return avail;
94}
95
96
97
98void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf)
99{
100	/* dvb_ringbuffer_flush() counts as read operation
101	 * smp_load_acquire() to load write pointer
102	 * smp_store_release() to update read pointer, this ensures that the
103	 * correct pointer is visible for subsequent dvb_ringbuffer_free()
104	 * calls on other cpu cores
105	 */
106	smp_store_release(&rbuf->pread, smp_load_acquire(&rbuf->pwrite));
107	rbuf->error = 0;
108}
109EXPORT_SYMBOL(dvb_ringbuffer_flush);
110
111void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf)
112{
113	/* dvb_ringbuffer_reset() counts as read and write operation
114	 * smp_store_release() to update read pointer
115	 */
116	smp_store_release(&rbuf->pread, 0);
117	/* smp_store_release() to update write pointer */
118	smp_store_release(&rbuf->pwrite, 0);
119	rbuf->error = 0;
120}
121
122void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf)
123{
124	unsigned long flags;
125
126	spin_lock_irqsave(&rbuf->lock, flags);
127	dvb_ringbuffer_flush(rbuf);
128	spin_unlock_irqrestore(&rbuf->lock, flags);
129
130	wake_up(&rbuf->queue);
131}
132
133ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer *rbuf, u8 __user *buf, size_t len)
134{
135	size_t todo = len;
136	size_t split;
137
138	split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
139	if (split > 0) {
140		if (copy_to_user(buf, rbuf->data+rbuf->pread, split))
141			return -EFAULT;
142		buf += split;
143		todo -= split;
144		/* smp_store_release() for read pointer update to ensure
145		 * that buf is not overwritten until read is complete,
146		 * this pairs with READ_ONCE() in dvb_ringbuffer_free()
147		 */
148		smp_store_release(&rbuf->pread, 0);
149	}
150	if (copy_to_user(buf, rbuf->data+rbuf->pread, todo))
151		return -EFAULT;
152
153	/* smp_store_release() to update read pointer, see above */
154	smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size);
155
156	return len;
157}
158
159void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf, size_t len)
160{
161	size_t todo = len;
162	size_t split;
163
164	split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
165	if (split > 0) {
166		memcpy(buf, rbuf->data+rbuf->pread, split);
167		buf += split;
168		todo -= split;
169		/* smp_store_release() for read pointer update to ensure
170		 * that buf is not overwritten until read is complete,
171		 * this pairs with READ_ONCE() in dvb_ringbuffer_free()
172		 */
173		smp_store_release(&rbuf->pread, 0);
174	}
175	memcpy(buf, rbuf->data+rbuf->pread, todo);
176
177	/* smp_store_release() to update read pointer, see above */
178	smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size);
179}
180
181
182ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf, size_t len)
183{
184	size_t todo = len;
185	size_t split;
186
187	split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
188
189	if (split > 0) {
190		memcpy(rbuf->data+rbuf->pwrite, buf, split);
191		buf += split;
192		todo -= split;
193		/* smp_store_release() for write pointer update to ensure that
194		 * written data is visible on other cpu cores before the pointer
195		 * update, this pairs with smp_load_acquire() in
196		 * dvb_ringbuffer_empty() or dvb_ringbuffer_avail()
197		 */
198		smp_store_release(&rbuf->pwrite, 0);
199	}
200	memcpy(rbuf->data+rbuf->pwrite, buf, todo);
201	/* smp_store_release() for write pointer update, see above */
202	smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size);
203
204	return len;
205}
206
207ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
208				  const u8 __user *buf, size_t len)
209{
210	int status;
211	size_t todo = len;
212	size_t split;
213
214	split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
215
216	if (split > 0) {
217		status = copy_from_user(rbuf->data+rbuf->pwrite, buf, split);
218		if (status)
219			return len - todo;
220		buf += split;
221		todo -= split;
222		/* smp_store_release() for write pointer update to ensure that
223		 * written data is visible on other cpu cores before the pointer
224		 * update, this pairs with smp_load_acquire() in
225		 * dvb_ringbuffer_empty() or dvb_ringbuffer_avail()
226		 */
227		smp_store_release(&rbuf->pwrite, 0);
228	}
229	status = copy_from_user(rbuf->data+rbuf->pwrite, buf, todo);
230	if (status)
231		return len - todo;
232	/* smp_store_release() for write pointer update, see above */
233	smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size);
234
235	return len;
236}
237
238ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf, size_t len)
239{
240	int status;
241	ssize_t oldpwrite = rbuf->pwrite;
242
243	DVB_RINGBUFFER_WRITE_BYTE(rbuf, len >> 8);
244	DVB_RINGBUFFER_WRITE_BYTE(rbuf, len & 0xff);
245	DVB_RINGBUFFER_WRITE_BYTE(rbuf, PKT_READY);
246	status = dvb_ringbuffer_write(rbuf, buf, len);
247
248	if (status < 0) rbuf->pwrite = oldpwrite;
249	return status;
250}
251
252ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf, size_t idx,
253				int offset, u8 __user *buf, size_t len)
254{
255	size_t todo;
256	size_t split;
257	size_t pktlen;
258
259	pktlen = rbuf->data[idx] << 8;
260	pktlen |= rbuf->data[(idx + 1) % rbuf->size];
261	if (offset > pktlen) return -EINVAL;
262	if ((offset + len) > pktlen) len = pktlen - offset;
263
264	idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
265	todo = len;
266	split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
267	if (split > 0) {
268		if (copy_to_user(buf, rbuf->data+idx, split))
269			return -EFAULT;
270		buf += split;
271		todo -= split;
272		idx = 0;
273	}
274	if (copy_to_user(buf, rbuf->data+idx, todo))
275		return -EFAULT;
276
277	return len;
278}
279
280ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
281				int offset, u8* buf, size_t len)
282{
283	size_t todo;
284	size_t split;
285	size_t pktlen;
286
287	pktlen = rbuf->data[idx] << 8;
288	pktlen |= rbuf->data[(idx + 1) % rbuf->size];
289	if (offset > pktlen) return -EINVAL;
290	if ((offset + len) > pktlen) len = pktlen - offset;
291
292	idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
293	todo = len;
294	split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
295	if (split > 0) {
296		memcpy(buf, rbuf->data+idx, split);
297		buf += split;
298		todo -= split;
299		idx = 0;
300	}
301	memcpy(buf, rbuf->data+idx, todo);
302	return len;
303}
304
305void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx)
306{
307	size_t pktlen;
308
309	rbuf->data[(idx + 2) % rbuf->size] = PKT_DISPOSED;
310
311	// clean up disposed packets
312	while(dvb_ringbuffer_avail(rbuf) > DVB_RINGBUFFER_PKTHDRSIZE) {
313		if (DVB_RINGBUFFER_PEEK(rbuf, 2) == PKT_DISPOSED) {
314			pktlen = DVB_RINGBUFFER_PEEK(rbuf, 0) << 8;
315			pktlen |= DVB_RINGBUFFER_PEEK(rbuf, 1);
316			DVB_RINGBUFFER_SKIP(rbuf, pktlen + DVB_RINGBUFFER_PKTHDRSIZE);
317		} else {
318			// first packet is not disposed, so we stop cleaning now
319			break;
320		}
321	}
322}
323
324ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen)
325{
326	int consumed;
327	int curpktlen;
328	int curpktstatus;
329
330	if (idx == -1) {
331	       idx = rbuf->pread;
332	} else {
333		curpktlen = rbuf->data[idx] << 8;
334		curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
335		idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
336	}
337
338	consumed = (idx - rbuf->pread);
339	if (consumed < 0)
340		consumed += rbuf->size;
341
342	while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {
343
344		curpktlen = rbuf->data[idx] << 8;
345		curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
346		curpktstatus = rbuf->data[(idx + 2) % rbuf->size];
347
348		if (curpktstatus == PKT_READY) {
349			*pktlen = curpktlen;
350			return idx;
351		}
352
353		consumed += curpktlen + DVB_RINGBUFFER_PKTHDRSIZE;
354		idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
355	}
356
357	// no packets available
358	return -1;
359}
360
361
362
363EXPORT_SYMBOL(dvb_ringbuffer_init);
364EXPORT_SYMBOL(dvb_ringbuffer_empty);
365EXPORT_SYMBOL(dvb_ringbuffer_free);
366EXPORT_SYMBOL(dvb_ringbuffer_avail);
367EXPORT_SYMBOL(dvb_ringbuffer_flush_spinlock_wakeup);
368EXPORT_SYMBOL(dvb_ringbuffer_read_user);
369EXPORT_SYMBOL(dvb_ringbuffer_read);
370EXPORT_SYMBOL(dvb_ringbuffer_write);
371EXPORT_SYMBOL(dvb_ringbuffer_write_user);
372