[media] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer

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@kolumbus.fi>
Acked-by: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c
index 4a88a3e..faa3671 100644 (file)
--- 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)