3 * dvb_ringbuffer.c: ring buffer implementation for the dvb driver
5 * Copyright (C) 2003 Oliver Endriss
6 * Copyright (C) 2004 Andrew de Quincey
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
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.
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.
22 * You should have received a copy of the GNU Lesser General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
29 #include <linux/errno.h>
30 #include <linux/kernel.h>
31 #include <linux/module.h>
32 #include <linux/sched.h>
33 #include <linux/string.h>
34 #include <asm/uaccess.h>
36 #include "dvb_ringbuffer.h"
39 #define PKT_DISPOSED 1
42 void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len)
44 rbuf->pread=rbuf->pwrite=0;
49 init_waitqueue_head(&rbuf->queue);
51 spin_lock_init(&(rbuf->lock));
56 int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf)
58 /* smp_load_acquire() to load write pointer on reader side
59 * this pairs with smp_store_release() in dvb_ringbuffer_write(),
60 * dvb_ringbuffer_write_user(), or dvb_ringbuffer_reset()
62 * for memory barriers also see Documentation/circular-buffers.txt
64 return (rbuf->pread == smp_load_acquire(&rbuf->pwrite));
69 ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf)
73 /* ACCESS_ONCE() to load read pointer on writer side
74 * this pairs with smp_store_release() in dvb_ringbuffer_read(),
75 * dvb_ringbuffer_read_user(), dvb_ringbuffer_flush(),
76 * or dvb_ringbuffer_reset()
78 free = ACCESS_ONCE(rbuf->pread) - rbuf->pwrite;
86 ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf)
90 /* smp_load_acquire() to load write pointer on reader side
91 * this pairs with smp_store_release() in dvb_ringbuffer_write(),
92 * dvb_ringbuffer_write_user(), or dvb_ringbuffer_reset()
94 avail = smp_load_acquire(&rbuf->pwrite) - rbuf->pread;
102 void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf)
104 /* dvb_ringbuffer_flush() counts as read operation
105 * smp_load_acquire() to load write pointer
106 * smp_store_release() to update read pointer, this ensures that the
107 * correct pointer is visible for subsequent dvb_ringbuffer_free()
108 * calls on other cpu cores
110 smp_store_release(&rbuf->pread, smp_load_acquire(&rbuf->pwrite));
113 EXPORT_SYMBOL(dvb_ringbuffer_flush);
115 void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf)
117 /* dvb_ringbuffer_reset() counts as read and write operation
118 * smp_store_release() to update read pointer
120 smp_store_release(&rbuf->pread, 0);
121 /* smp_store_release() to update write pointer */
122 smp_store_release(&rbuf->pwrite, 0);
126 void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf)
130 spin_lock_irqsave(&rbuf->lock, flags);
131 dvb_ringbuffer_flush(rbuf);
132 spin_unlock_irqrestore(&rbuf->lock, flags);
134 wake_up(&rbuf->queue);
137 ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer *rbuf, u8 __user *buf, size_t len)
142 split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
144 if (copy_to_user(buf, rbuf->data+rbuf->pread, split))
148 /* smp_store_release() for read pointer update to ensure
149 * that buf is not overwritten until read is complete,
150 * this pairs with ACCESS_ONCE() in dvb_ringbuffer_free()
152 smp_store_release(&rbuf->pread, 0);
154 if (copy_to_user(buf, rbuf->data+rbuf->pread, todo))
157 /* smp_store_release() to update read pointer, see above */
158 smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size);
163 void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf, size_t len)
168 split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
170 memcpy(buf, rbuf->data+rbuf->pread, split);
173 /* smp_store_release() for read pointer update to ensure
174 * that buf is not overwritten until read is complete,
175 * this pairs with ACCESS_ONCE() in dvb_ringbuffer_free()
177 smp_store_release(&rbuf->pread, 0);
179 memcpy(buf, rbuf->data+rbuf->pread, todo);
181 /* smp_store_release() to update read pointer, see above */
182 smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size);
186 ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf, size_t len)
191 split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
194 memcpy(rbuf->data+rbuf->pwrite, buf, split);
197 /* smp_store_release() for write pointer update to ensure that
198 * written data is visible on other cpu cores before the pointer
199 * update, this pairs with smp_load_acquire() in
200 * dvb_ringbuffer_empty() or dvb_ringbuffer_avail()
202 smp_store_release(&rbuf->pwrite, 0);
204 memcpy(rbuf->data+rbuf->pwrite, buf, todo);
205 /* smp_store_release() for write pointer update, see above */
206 smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size);
211 ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
212 const u8 __user *buf, size_t len)
218 split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
221 status = copy_from_user(rbuf->data+rbuf->pwrite, buf, split);
226 /* smp_store_release() for write pointer update to ensure that
227 * written data is visible on other cpu cores before the pointer
228 * update, this pairs with smp_load_acquire() in
229 * dvb_ringbuffer_empty() or dvb_ringbuffer_avail()
231 smp_store_release(&rbuf->pwrite, 0);
233 status = copy_from_user(rbuf->data+rbuf->pwrite, buf, todo);
236 /* smp_store_release() for write pointer update, see above */
237 smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size);
242 ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf, size_t len)
245 ssize_t oldpwrite = rbuf->pwrite;
247 DVB_RINGBUFFER_WRITE_BYTE(rbuf, len >> 8);
248 DVB_RINGBUFFER_WRITE_BYTE(rbuf, len & 0xff);
249 DVB_RINGBUFFER_WRITE_BYTE(rbuf, PKT_READY);
250 status = dvb_ringbuffer_write(rbuf, buf, len);
252 if (status < 0) rbuf->pwrite = oldpwrite;
256 ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf, size_t idx,
257 int offset, u8 __user *buf, size_t len)
263 pktlen = rbuf->data[idx] << 8;
264 pktlen |= rbuf->data[(idx + 1) % rbuf->size];
265 if (offset > pktlen) return -EINVAL;
266 if ((offset + len) > pktlen) len = pktlen - offset;
268 idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
270 split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
272 if (copy_to_user(buf, rbuf->data+idx, split))
278 if (copy_to_user(buf, rbuf->data+idx, todo))
284 ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
285 int offset, u8* buf, size_t len)
291 pktlen = rbuf->data[idx] << 8;
292 pktlen |= rbuf->data[(idx + 1) % rbuf->size];
293 if (offset > pktlen) return -EINVAL;
294 if ((offset + len) > pktlen) len = pktlen - offset;
296 idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
298 split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
300 memcpy(buf, rbuf->data+idx, split);
305 memcpy(buf, rbuf->data+idx, todo);
309 void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx)
313 rbuf->data[(idx + 2) % rbuf->size] = PKT_DISPOSED;
315 // clean up disposed packets
316 while(dvb_ringbuffer_avail(rbuf) > DVB_RINGBUFFER_PKTHDRSIZE) {
317 if (DVB_RINGBUFFER_PEEK(rbuf, 2) == PKT_DISPOSED) {
318 pktlen = DVB_RINGBUFFER_PEEK(rbuf, 0) << 8;
319 pktlen |= DVB_RINGBUFFER_PEEK(rbuf, 1);
320 DVB_RINGBUFFER_SKIP(rbuf, pktlen + DVB_RINGBUFFER_PKTHDRSIZE);
322 // first packet is not disposed, so we stop cleaning now
328 ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen)
337 curpktlen = rbuf->data[idx] << 8;
338 curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
339 idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
342 consumed = (idx - rbuf->pread) % rbuf->size;
344 while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {
346 curpktlen = rbuf->data[idx] << 8;
347 curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
348 curpktstatus = rbuf->data[(idx + 2) % rbuf->size];
350 if (curpktstatus == PKT_READY) {
355 consumed += curpktlen + DVB_RINGBUFFER_PKTHDRSIZE;
356 idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
359 // no packets available
365 EXPORT_SYMBOL(dvb_ringbuffer_init);
366 EXPORT_SYMBOL(dvb_ringbuffer_empty);
367 EXPORT_SYMBOL(dvb_ringbuffer_free);
368 EXPORT_SYMBOL(dvb_ringbuffer_avail);
369 EXPORT_SYMBOL(dvb_ringbuffer_flush_spinlock_wakeup);
370 EXPORT_SYMBOL(dvb_ringbuffer_read_user);
371 EXPORT_SYMBOL(dvb_ringbuffer_read);
372 EXPORT_SYMBOL(dvb_ringbuffer_write);
373 EXPORT_SYMBOL(dvb_ringbuffer_write_user);