[PATCH 4/5] ALSA: firewire-lib: fix calculation for size of IR context payload

[Takashi Sakamoto]

The quadlets for CIP header is handled as a part of IR context header,
thus it doesn't join in IR context payload. However current calculation
includes the quadlets in IR context payload.

Cc: <stable at vger.kernel.org>
Fixes: f11453c7cc01 ("ALSA: firewire-lib: use 16 bytes IR context header to separate CIP header")
Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 sound/firewire/amdtp-stream.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index b53971bf4b90..73aff017dc9a 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -1071,23 +1071,22 @@ static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
 		s->data_block_counter = 0;
 	}
 
-	/* initialize packet buffer */
+	// initialize packet buffer.
+	max_ctx_payload_size = amdtp_stream_get_max_payload(s);
 	if (s->direction == AMDTP_IN_STREAM) {
 		dir = DMA_FROM_DEVICE;
 		type = FW_ISO_CONTEXT_RECEIVE;
-		if (!(s->flags & CIP_NO_HEADER))
+		if (!(s->flags & CIP_NO_HEADER)) {
+			max_ctx_payload_size -= 8;
 			ctx_header_size = IR_CTX_HEADER_SIZE_CIP;
-		else
+		} else {
 			ctx_header_size = IR_CTX_HEADER_SIZE_NO_CIP;
-
-		max_ctx_payload_size = amdtp_stream_get_max_payload(s) -
-				       ctx_header_size;
+		}
 	} else {
 		dir = DMA_TO_DEVICE;
 		type = FW_ISO_CONTEXT_TRANSMIT;
 		ctx_header_size = 0;	// No effect for IT context.
 
-		max_ctx_payload_size = amdtp_stream_get_max_payload(s);
 		if (!(s->flags & CIP_NO_HEADER))
 			max_ctx_payload_size -= IT_PKT_HEADER_SIZE_CIP;
 	}
-- 
2.27.0