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
dvb_ringbuffer_init(struct dvb_ringbuffer * rbuf,void * data,size_t len)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
dvb_ringbuffer_empty(struct dvb_ringbuffer * rbuf)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
dvb_ringbuffer_free(struct dvb_ringbuffer * rbuf)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
dvb_ringbuffer_avail(struct dvb_ringbuffer * rbuf)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
dvb_ringbuffer_flush(struct dvb_ringbuffer * rbuf)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
dvb_ringbuffer_reset(struct dvb_ringbuffer * rbuf)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
dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer * rbuf)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
dvb_ringbuffer_read_user(struct dvb_ringbuffer * rbuf,u8 __user * buf,size_t len)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
dvb_ringbuffer_read(struct dvb_ringbuffer * rbuf,u8 * buf,size_t len)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
dvb_ringbuffer_write(struct dvb_ringbuffer * rbuf,const u8 * buf,size_t len)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
dvb_ringbuffer_write_user(struct dvb_ringbuffer * rbuf,const u8 __user * buf,size_t len)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
dvb_ringbuffer_pkt_write(struct dvb_ringbuffer * rbuf,u8 * buf,size_t len)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
dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer * rbuf,size_t idx,int offset,u8 __user * buf,size_t len)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
dvb_ringbuffer_pkt_read(struct dvb_ringbuffer * rbuf,size_t idx,int offset,u8 * buf,size_t len)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
dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer * rbuf,size_t idx)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
dvb_ringbuffer_pkt_next(struct dvb_ringbuffer * rbuf,size_t idx,size_t * pktlen)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