media: dvb: Fix calculation of next ready packet in dvb-ringbuffer

The calculation of number of bytes between the last reported
packet to the user and the current read pointer did not properly
take into account wrap-around case in the packet buffer.
Debug printouts for values returned by dvb-ringbuffer were
added for better traceability.

CRs-Fixed: 470982
Change-Id: I2765f5b1e0fbb7baed6725f2617702dd7ed87556
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>
diff --git a/drivers/media/dvb/dvb-core/dvb_ringbuffer.c b/drivers/media/dvb/dvb-core/dvb_ringbuffer.c
index 92f7463..e8480f7 100644
--- a/drivers/media/dvb/dvb-core/dvb_ringbuffer.c
+++ b/drivers/media/dvb/dvb-core/dvb_ringbuffer.c
@@ -5,7 +5,7 @@
  * Copyright (C) 2003 Oliver Endriss
  * Copyright (C) 2004 Andrew de Quincey
  *
- * Copyright (c) 2012, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
  *
  * based on code originally found in av7110.c & dvb_ci.c:
  * Copyright (C) 1999-2003 Ralph  Metzler
@@ -334,7 +334,10 @@
 		idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
 	}
 
-	consumed = (idx - rbuf->pread) % rbuf->size;
+	if (idx >= rbuf->pread)
+		consumed = idx - rbuf->pread;
+	else
+		consumed = rbuf->size - (rbuf->pread - idx);
 
 	while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {
 
diff --git a/drivers/media/dvb/mpq/demux/mpq_dmx_plugin_common.c b/drivers/media/dvb/mpq/demux/mpq_dmx_plugin_common.c
index aa5c0df..b5a7593 100644
--- a/drivers/media/dvb/mpq/demux/mpq_dmx_plugin_common.c
+++ b/drivers/media/dvb/mpq/demux/mpq_dmx_plugin_common.c
@@ -1231,6 +1231,8 @@
 		return -EPERM;
 	}
 
+	MPQ_DVB_DBG_PRINT("%s: cookie=%d\n", __func__, cookie);
+
 	if (cookie < 0) {
 		MPQ_DVB_ERR_PRINT("%s: invalid cookie parameter\n", __func__);
 		return -EINVAL;
@@ -2451,9 +2453,15 @@
 
 	data->data_length = 0;
 	data->buf.handle = packet->raw_data_handle;
+
 	/* this has to succeed when called here, after packet was written */
 	data->buf.cookie = mpq_streambuffer_pkt_next(stream_buffer,
 				feed_data->last_pkt_index, &len);
+	if (data->buf.cookie < 0)
+		MPQ_DVB_DBG_PRINT(
+			"%s: received invalid packet index %d\n",
+			__func__, data->buf.cookie);
+
 	data->buf.offset = packet->raw_data_offset;
 	data->buf.len = packet->raw_data_len;
 	data->buf.pts_exists = pts_dts->pts_exist;
@@ -2469,6 +2477,8 @@
 	/* save for next time: */
 	feed_data->last_pkt_index = data->buf.cookie;
 
+	MPQ_DVB_DBG_PRINT("%s: cookie=%d\n", __func__, data->buf.cookie);
+
 	/* reset counters */
 	feed_data->ts_packets_num = 0;
 	feed_data->ts_dropped_bytes = 0;
@@ -4247,7 +4257,12 @@
 				__func__, ret);
 		}
 		mpq_dmx_update_decoder_stat(mpq_demux);
-		mpq_streambuffer_pkt_write(sbuf, &packet, (u8 *)&meta_data);
+		if (mpq_streambuffer_pkt_write(sbuf,
+				&packet,
+				(u8 *)&meta_data) < 0)
+			MPQ_DVB_ERR_PRINT(
+				"%s: Couldn't write packet. Should never happen\n",
+				__func__);
 
 		if (generate_es_events) {
 			struct dmx_data_ready data;