Avoid unnecessary DVB TS 188 sized packet copying from DMA buffer into stack. Backtrack one 188 sized packet just after some garbage bytes when possible. This obsoletes patch https://patchwork.kernel.org/patch/118147/ Signed-off-by: Marko Ristola marko.ristola@xxxxxxxxxxx diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c index 4a88a3e..faa3671 100644 --- a/drivers/media/dvb/dvb-core/dvb_demux.c +++ b/drivers/media/dvb/dvb-core/dvb_demux.c @@ -478,97 +478,94 @@ void dvb_dmx_swfilter_packets(struct dvb_demux *demux, const u8 *buf, EXPORT_SYMBOL(dvb_dmx_swfilter_packets); -void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count) +static inline int find_next_packet(const u8 *buf, int pos, size_t count, + const int pktsize) { - int p = 0, i, j; + int start = pos, lost; - spin_lock(&demux->lock); - - if (demux->tsbufp) { - i = demux->tsbufp; - j = 188 - i; - if (count < j) { - memcpy(&demux->tsbuf[i], buf, count); - demux->tsbufp += count; - goto bailout; - } - memcpy(&demux->tsbuf[i], buf, j); - if (demux->tsbuf[0] == 0x47) - dvb_dmx_swfilter_packet(demux, demux->tsbuf); - demux->tsbufp = 0; - p += j; + while (pos < count) { + if (buf[pos] == 0x47 || + (pktsize == 204 && buf[pos] == 0xB8)) + break; + pos++; } - while (p < count) { - if (buf[p] == 0x47) { - if (count - p >= 188) { - dvb_dmx_swfilter_packet(demux, &buf[p]); - p += 188; - } else { - i = count - p; - memcpy(demux->tsbuf, &buf[p], i); - demux->tsbufp = i; - goto bailout; - } - } else - p++; + lost = pos - start; + if (lost) { + /* This garbage is part of a valid packet? */ + int backtrack = pos - pktsize; + if (backtrack >= 0 && (buf[backtrack] == 0x47 || + (pktsize == 204 && buf[backtrack] == 0xB8))) + return backtrack; } -bailout: - spin_unlock(&demux->lock); + return pos; } -EXPORT_SYMBOL(dvb_dmx_swfilter); - -void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t count) +/* Filter all pktsize= 188 or 204 sized packets and skip garbage. */ +static inline void _dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, + size_t count, const int pktsize) { int p = 0, i, j; - u8 tmppack[188]; + const u8 *q; spin_lock(&demux->lock); - if (demux->tsbufp) { + if (demux->tsbufp) { /* tsbuf[0] is now 0x47. */ i = demux->tsbufp; - j = 204 - i; + j = pktsize - i; if (count < j) { memcpy(&demux->tsbuf[i], buf, count); demux->tsbufp += count; goto bailout; } memcpy(&demux->tsbuf[i], buf, j); - if ((demux->tsbuf[0] == 0x47) || (demux->tsbuf[0] == 0xB8)) { - memcpy(tmppack, demux->tsbuf, 188); - if (tmppack[0] == 0xB8) - tmppack[0] = 0x47; - dvb_dmx_swfilter_packet(demux, tmppack); - } + if (demux->tsbuf[0] == 0x47) /* double check */ + dvb_dmx_swfilter_packet(demux, demux->tsbuf); demux->tsbufp = 0; p += j; } - while (p < count) { - if ((buf[p] == 0x47) || (buf[p] == 0xB8)) { - if (count - p >= 204) { - memcpy(tmppack, &buf[p], 188); - if (tmppack[0] == 0xB8) - tmppack[0] = 0x47; - dvb_dmx_swfilter_packet(demux, tmppack); - p += 204; - } else { - i = count - p; - memcpy(demux->tsbuf, &buf[p], i); - demux->tsbufp = i; - goto bailout; - } - } else { - p++; + while (1) { + p = find_next_packet(buf, p, count, pktsize); + if (p >= count) + break; + if (count - p < pktsize) + break; + + q = &buf[p]; + + if (pktsize == 204 && (*q == 0xB8)) { + memcpy(demux->tsbuf, q, 188); + demux->tsbuf[0] = 0x47; + q = demux->tsbuf; } + dvb_dmx_swfilter_packet(demux, q); + p += pktsize; + } + + i = count - p; + if (i) { + memcpy(demux->tsbuf, &buf[p], i); + demux->tsbufp = i; + if (pktsize == 204 && demux->tsbuf[0] == 0xB8) + demux->tsbuf[0] = 0x47; } bailout: spin_unlock(&demux->lock); } +void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count) +{ + _dvb_dmx_swfilter(demux, buf, count, 188); +} +EXPORT_SYMBOL(dvb_dmx_swfilter); + +void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t count) +{ + _dvb_dmx_swfilter(demux, buf, count, 204); +} EXPORT_SYMBOL(dvb_dmx_swfilter_204); static struct dvb_demux_filter *dvb_dmx_filter_alloc(struct dvb_demux *demux) -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
