[media] cec: fix report_current_latency

In the (very) small print of the REPORT_CURRENT_LATENCY message there is a
line that says that the last byte of the message (audio out delay) is only
present if the 'audio out compensated' value is 3.

I missed this, and so if this message was sent with a total length of 6 (i.e.
without the audio out delay byte), then it was rejected by the framework
since a minimum length of 7 was expected.

Fix this minimum length check and update the wrappers in cec-funcs.h to do
the right thing based on the message length.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/cec/cec-adap.c

@@ -851,7 +851,7 @@ static const u8 cec_msg_size[256] = {
 	[CEC_MSG_REQUEST_ARC_TERMINATION] = 2 | DIRECTED,
 	[CEC_MSG_TERMINATE_ARC] = 2 | DIRECTED,
 	[CEC_MSG_REQUEST_CURRENT_LATENCY] = 4 | BCAST,
-	[CEC_MSG_REPORT_CURRENT_LATENCY] = 7 | BCAST,
+	[CEC_MSG_REPORT_CURRENT_LATENCY] = 6 | BCAST,
 	[CEC_MSG_CDC_MESSAGE] = 2 | BCAST,
 };
 

include/uapi/linux/cec-funcs.h

@@ -1665,14 +1665,15 @@ static inline void cec_msg_report_current_latency(struct cec_msg *msg,
 						  __u8 audio_out_compensated,
 						  __u8 audio_out_delay)
 {
-	msg->len = 7;
+	msg->len = 6;
 	msg->msg[0] |= 0xf; /* broadcast */
 	msg->msg[1] = CEC_MSG_REPORT_CURRENT_LATENCY;
 	msg->msg[2] = phys_addr >> 8;
 	msg->msg[3] = phys_addr & 0xff;
 	msg->msg[4] = video_latency;
 	msg->msg[5] = (low_latency_mode << 2) | audio_out_compensated;
-	msg->msg[6] = audio_out_delay;
+	if (audio_out_compensated == 3)
+		msg->msg[msg->len++] = audio_out_delay;
 }
 
 static inline void cec_ops_report_current_latency(const struct cec_msg *msg,
@@ -1686,7 +1687,10 @@ static inline void cec_ops_report_current_latency(const struct cec_msg *msg,
 	*video_latency = msg->msg[4];
 	*low_latency_mode = (msg->msg[5] >> 2) & 1;
 	*audio_out_compensated = msg->msg[5] & 3;
+	if (*audio_out_compensated == 3 && msg->len >= 7)
 		*audio_out_delay = msg->msg[6];
+	else
+		*audio_out_delay = 0;
 }
 
 static inline void cec_msg_request_current_latency(struct cec_msg *msg,