drivers/media/dvb-core/dvb_ringbuffer.c

   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  * 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.
  25  */
  26
  27
  28
  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 <linux/uaccess.h>
  35
  36 #include "dvb_ringbuffer.h"
  37
  38 #define PKT_READY 0
  39 #define PKT_DISPOSED 1
  40
  41
  42 void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len)
  43 {
  44         rbuf->pread=rbuf->pwrite=0;
  45         rbuf->data=data;
  46         rbuf->size=len;
  47         rbuf->error=0;
  48
  49         init_waitqueue_head(&rbuf->queue);
  50
  51         spin_lock_init(&(rbuf->lock));
  52 }
  53
  54
  55
  56 int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf)
  57 {
  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()
  61          *
  62          * for memory barriers also see Documentation/circular-buffers.txt
  63          */
  64         return (rbuf->pread == smp_load_acquire(&rbuf->pwrite));
  65 }
  66
  67
  68
  69 ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf)
  70 {
  71         ssize_t free;
  72
  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()
  77          */
  78         free = ACCESS_ONCE(rbuf->pread) - rbuf->pwrite;
  79         if (free <= 0)
  80                 free += rbuf->size;
  81         return free-1;
  82 }
  83
  84
  85
  86 ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf)
  87 {
  88         ssize_t avail;
  89
  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()
  93          */
  94         avail = smp_load_acquire(&rbuf->pwrite) - rbuf->pread;
  95         if (avail < 0)
  96                 avail += rbuf->size;
  97         return avail;
  98 }
  99
 100
 101
 102 void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf)
 103 {
 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
 109          */
 110         smp_store_release(&rbuf->pread, smp_load_acquire(&rbuf->pwrite));
 111         rbuf->error = 0;
 112 }
 113 EXPORT_SYMBOL(dvb_ringbuffer_flush);
 114
 115 void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf)
 116 {
 117         /* dvb_ringbuffer_reset() counts as read and write operation
 118          * smp_store_release() to update read pointer
 119          */
 120         smp_store_release(&rbuf->pread, 0);
 121         /* smp_store_release() to update write pointer */
 122         smp_store_release(&rbuf->pwrite, 0);
 123         rbuf->error = 0;
 124 }
 125
 126 void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf)
 127 {
 128         unsigned long flags;
 129
 130         spin_lock_irqsave(&rbuf->lock, flags);
 131         dvb_ringbuffer_flush(rbuf);
 132         spin_unlock_irqrestore(&rbuf->lock, flags);
 133
 134         wake_up(&rbuf->queue);
 135 }
 136
 137 ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer *rbuf, u8 __user *buf, size_t len)
 138 {
 139         size_t todo = len;
 140         size_t split;
 141
 142         split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
 143         if (split > 0) {
 144                 if (copy_to_user(buf, rbuf->data+rbuf->pread, split))
 145                         return -EFAULT;
 146                 buf += split;
 147                 todo -= 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()
 151                  */
 152                 smp_store_release(&rbuf->pread, 0);
 153         }
 154         if (copy_to_user(buf, rbuf->data+rbuf->pread, todo))
 155                 return -EFAULT;
 156
 157         /* smp_store_release() to update read pointer, see above */
 158         smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size);
 159
 160         return len;
 161 }
 162
 163 void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf, size_t len)
 164 {
 165         size_t todo = len;
 166         size_t split;
 167
 168         split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
 169         if (split > 0) {
 170                 memcpy(buf, rbuf->data+rbuf->pread, split);
 171                 buf += split;
 172                 todo -= 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()
 176                  */
 177                 smp_store_release(&rbuf->pread, 0);
 178         }
 179         memcpy(buf, rbuf->data+rbuf->pread, todo);
 180
 181         /* smp_store_release() to update read pointer, see above */
 182         smp_store_release(&rbuf->pread, (rbuf->pread + todo) % rbuf->size);
 183 }
 184
 185
 186 ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf, size_t len)
 187 {
 188         size_t todo = len;
 189         size_t split;
 190
 191         split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
 192
 193         if (split > 0) {
 194                 memcpy(rbuf->data+rbuf->pwrite, buf, split);
 195                 buf += split;
 196                 todo -= 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()
 201                  */
 202                 smp_store_release(&rbuf->pwrite, 0);
 203         }
 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);
 207
 208         return len;
 209 }
 210
 211 ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
 212                                   const u8 __user *buf, size_t len)
 213 {
 214         int status;
 215         size_t todo = len;
 216         size_t split;
 217
 218         split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
 219
 220         if (split > 0) {
 221                 status = copy_from_user(rbuf->data+rbuf->pwrite, buf, split);
 222                 if (status)
 223                         return len - todo;
 224                 buf += split;
 225                 todo -= 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()
 230                  */
 231                 smp_store_release(&rbuf->pwrite, 0);
 232         }
 233         status = copy_from_user(rbuf->data+rbuf->pwrite, buf, todo);
 234         if (status)
 235                 return len - todo;
 236         /* smp_store_release() for write pointer update, see above */
 237         smp_store_release(&rbuf->pwrite, (rbuf->pwrite + todo) % rbuf->size);
 238
 239         return len;
 240 }
 241
 242 ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf, size_t len)
 243 {
 244         int status;
 245         ssize_t oldpwrite = rbuf->pwrite;
 246
 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);
 251
 252         if (status < 0) rbuf->pwrite = oldpwrite;
 253         return status;
 254 }
 255
 256 ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf, size_t idx,
 257                                 int offset, u8 __user *buf, size_t len)
 258 {
 259         size_t todo;
 260         size_t split;
 261         size_t pktlen;
 262
 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;
 267
 268         idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
 269         todo = len;
 270         split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
 271         if (split > 0) {
 272                 if (copy_to_user(buf, rbuf->data+idx, split))
 273                         return -EFAULT;
 274                 buf += split;
 275                 todo -= split;
 276                 idx = 0;
 277         }
 278         if (copy_to_user(buf, rbuf->data+idx, todo))
 279                 return -EFAULT;
 280
 281         return len;
 282 }
 283
 284 ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
 285                                 int offset, u8* buf, size_t len)
 286 {
 287         size_t todo;
 288         size_t split;
 289         size_t pktlen;
 290
 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;
 295
 296         idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
 297         todo = len;
 298         split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
 299         if (split > 0) {
 300                 memcpy(buf, rbuf->data+idx, split);
 301                 buf += split;
 302                 todo -= split;
 303                 idx = 0;
 304         }
 305         memcpy(buf, rbuf->data+idx, todo);
 306         return len;
 307 }
 308
 309 void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx)
 310 {
 311         size_t pktlen;
 312
 313         rbuf->data[(idx + 2) % rbuf->size] = PKT_DISPOSED;
 314
 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);
 321                 } else {
 322                         // first packet is not disposed, so we stop cleaning now
 323                         break;
 324                 }
 325         }
 326 }
 327
 328 ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen)
 329 {
 330         int consumed;
 331         int curpktlen;
 332         int curpktstatus;
 333
 334         if (idx == -1) {
 335                idx = rbuf->pread;
 336         } else {
 337                 curpktlen = rbuf->data[idx] << 8;
 338                 curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
 339                 idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
 340         }
 341
 342         consumed = (idx - rbuf->pread) % rbuf->size;
 343
 344         while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {
 345
 346                 curpktlen = rbuf->data[idx] << 8;
 347                 curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
 348                 curpktstatus = rbuf->data[(idx + 2) % rbuf->size];
 349
 350                 if (curpktstatus == PKT_READY) {
 351                         *pktlen = curpktlen;
 352                         return idx;
 353                 }
 354
 355                 consumed += curpktlen + DVB_RINGBUFFER_PKTHDRSIZE;
 356                 idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
 357         }
 358
 359         // no packets available
 360         return -1;
 361 }
 362
 363
 364
 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);