V4L/DVB (10439): cx18: Clean-up and enable sliced VBI handling

Removed legacy ivtv state variables, added comments, and cleaned
up sliced VBI related code.  Enabled sliced VBI.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 43 insertions, 11 deletions

diff --git a/drivers/media/video/cx18/cx18-fileops.c b/drivers/media/video/cx18/cx18-fileops.c
index 23006f7d9159..0b1dbc67e1ab 100644
--- a/drivers/media/video/cx18/cx18-fileops.c
+++ b/drivers/media/video/cx18/cx18-fileops.c
@@ -176,6 +176,8 @@ static struct cx18_buffer *cx18_get_buffer(struct cx18_stream *s, int non_block,
         *err = 0;
         while (1) {
                 if (s->type == CX18_ENC_STREAM_TYPE_MPG) {
+                        /* Process pending program info updates and pending
+                           VBI data */
 
                         if (time_after(jiffies, cx->dualwatch_jiffies + msecs_to_jiffies(1000))) {
                                 cx->dualwatch_jiffies = jiffies;
@@ -260,6 +262,20 @@ static size_t cx18_copy_buf_to_user(struct cx18_stream *s,
                 len = ucount;
         if (cx->vbi.insert_mpeg && s->type == CX18_ENC_STREAM_TYPE_MPG &&
             !cx18_raw_vbi(cx) && buf != &cx->vbi.sliced_mpeg_buf) {
+                /*
+                 * Try to find a good splice point in the PS, just before
+                 * an MPEG-2 Program Pack start code, and provide only
+                 * up to that point to the user, so it's easy to insert VBI data
+                 * the next time around.
+                 */
+                /* FIXME - This only works for an MPEG-2 PS, not a TS */
+                /*
+                 * An MPEG-2 Program Stream (PS) is a series of
+                 * MPEG-2 Program Packs terminated by an
+                 * MPEG Program End Code after the last Program Pack.
+                 * A Program Pack may hold a PS System Header packet and any
+                 * number of Program Elementary Stream (PES) Packets
+                 */
                 const char *start = buf->buf + buf->readpos;
                 const char *p = start + 1;
                 const u8 *q;
@@ -267,38 +283,54 @@ static size_t cx18_copy_buf_to_user(struct cx18_stream *s,
                 int stuffing, i;
 
                 while (start + len > p) {
+                        /* Scan for a 0 to find a potential MPEG-2 start code */
                         q = memchr(p, 0, start + len - p);
                         if (q == NULL)
                                 break;
                         p = q + 1;
+                        /*
+                         * Keep looking if not a
+                         * MPEG-2 Pack header start code:  0x00 0x00 0x01 0xba
+                         * or MPEG-2 video PES start code: 0x00 0x00 0x01 0xe0
+                         */
                         if ((char *)q + 15 >= buf->buf + buf->bytesused ||
                             q[1] != 0 || q[2] != 1 || q[3] != ch)
                                 continue;
+
+                        /* If expecting the primary video PES */
                         if (!cx->search_pack_header) {
+                                /* Continue if it couldn't be a PES packet */
                                 if ((q[6] & 0xc0) != 0x80)
                                         continue;
-                                if (((q[7] & 0xc0) == 0x80 &&
-                                     (q[9] & 0xf0) == 0x20) ||
-                                    ((q[7] & 0xc0) == 0xc0 &&
-                                     (q[9] & 0xf0) == 0x30)) {
-                                        ch = 0xba;
+                                /* Check if a PTS or PTS & DTS follow */
+                                if (((q[7] & 0xc0) == 0x80 &&  /* PTS only */
+                                     (q[9] & 0xf0) == 0x20) || /* PTS only */
+                                    ((q[7] & 0xc0) == 0xc0 &&  /* PTS & DTS */
+                                     (q[9] & 0xf0) == 0x30)) { /* DTS follows */
+                                        /* Assume we found the video PES hdr */
+                                        ch = 0xba; /* next want a Program Pack*/
                                         cx->search_pack_header = 1;
-                                        p = q + 9;
+                                        p = q + 9; /* Skip this video PES hdr */
                                 }
                                 continue;
                         }
+
+                        /* We may have found a Program Pack start code */
+
+                        /* Get the count of stuffing bytes & verify them */
                         stuffing = q[13] & 7;
                         /* all stuffing bytes must be 0xff */
                         for (i = 0; i < stuffing; i++)
                                 if (q[14 + i] != 0xff)
                                         break;
-                        if (i == stuffing &&
-                            (q[4] & 0xc4) == 0x44 &&
-                            (q[12] & 3) == 3 &&
-                            q[14 + stuffing] == 0 &&
+                        if (i == stuffing && /* right number of stuffing bytes*/
+                            (q[4] & 0xc4) == 0x44 && /* marker check */
+                            (q[12] & 3) == 3 &&  /* marker check */
+                            q[14 + stuffing] == 0 && /* PES Pack or Sys Hdr */
                             q[15 + stuffing] == 0 &&
                             q[16 + stuffing] == 1) {
-                                cx->search_pack_header = 0;
+                                /* We declare we actually found a Program Pack*/
+                                cx->search_pack_header = 0; /* expect vid PES */
                                 len = (char *)q - start;
                                 cx18_setup_sliced_vbi_buf(cx);
                                 break;