372 lines · c
1/*2 *3 * dvb_ringbuffer.c: ring buffer implementation for the dvb driver4 *5 * Copyright (C) 2003 Oliver Endriss6 * Copyright (C) 2004 Andrew de Quincey7 *8 * based on code originally found in av7110.c & dvb_ci.c:9 * Copyright (C) 1999-2003 Ralph Metzler10 * & Marcus Metzler for convergence integrated media GmbH11 *12 * This program is free software; you can redistribute it and/or13 * modify it under the terms of the GNU Lesser General Public License14 * as published by the Free Software Foundation; either version 2.115 * 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 of19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the20 * 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 035#define PKT_DISPOSED 136 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 side55 * 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.rst59 */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 side70 * 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 side87 * 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 operation101 * smp_load_acquire() to load write pointer102 * smp_store_release() to update read pointer, this ensures that the103 * correct pointer is visible for subsequent dvb_ringbuffer_free()104 * calls on other cpu cores105 */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 operation114 * smp_store_release() to update read pointer115 */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 ensure145 * 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 ensure170 * 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 that194 * written data is visible on other cpu cores before the pointer195 * update, this pairs with smp_load_acquire() in196 * 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 that223 * written data is visible on other cpu cores before the pointer224 * update, this pairs with smp_load_acquire() in225 * 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 packets312 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 now319 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 available358 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