[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>

1 files changed, 57 insertions, 60 deletions

diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c
index 4a88a3e4db2b..faa3671b649e 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)