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 
38 void 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 
52 int 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 
65 ssize_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 
82 ssize_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 
98 void 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 }
109 EXPORT_SYMBOL(dvb_ringbuffer_flush);
110 
111 void 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 
122 void 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 
133 ssize_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 
159 void 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 
182 ssize_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 
207 ssize_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 
238 ssize_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 
252 ssize_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 
280 ssize_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 
305 void 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 
324 ssize_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) % rbuf->size;
339 
340 	while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {
341 
342 		curpktlen = rbuf->data[idx] << 8;
343 		curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
344 		curpktstatus = rbuf->data[(idx + 2) % rbuf->size];
345 
346 		if (curpktstatus == PKT_READY) {
347 			*pktlen = curpktlen;
348 			return idx;
349 		}
350 
351 		consumed += curpktlen + DVB_RINGBUFFER_PKTHDRSIZE;
352 		idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
353 	}
354 
355 	// no packets available
356 	return -1;
357 }
358 
359 
360 
361 EXPORT_SYMBOL(dvb_ringbuffer_init);
362 EXPORT_SYMBOL(dvb_ringbuffer_empty);
363 EXPORT_SYMBOL(dvb_ringbuffer_free);
364 EXPORT_SYMBOL(dvb_ringbuffer_avail);
365 EXPORT_SYMBOL(dvb_ringbuffer_flush_spinlock_wakeup);
366 EXPORT_SYMBOL(dvb_ringbuffer_read_user);
367 EXPORT_SYMBOL(dvb_ringbuffer_read);
368 EXPORT_SYMBOL(dvb_ringbuffer_write);
369 EXPORT_SYMBOL(dvb_ringbuffer_write_user);
370