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Commit f5580d8d authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
Browse files

[media] cec: accept two replies for CEC_MSG_INITIATE_ARC 



The CEC_MSG_INITIATE_ARC message is special since it is the ONLY
CEC message that accepts two possible valid replies:

CEC_MSG_REPORT_ARC_INITIATED and CEC_MSG_REPORT_ARC_TERMINATED.

So if the transmitted message is CEC_MSG_INITIATE_ARC and the remote
side replied with CEC_MSG_REPORT_ARC_INITIATED or CEC_MSG_REPORT_ARC_TERMINATED,
then a msg->reply value of CEC_MSG_REPORT_ARC_INITIATED or
CEC_MSG_REPORT_ARC_TERMINATED will match either reply.

I thought about either adding a second reply2 field, but that's ugly
for all other messages that have only one reply, and what if in the
future a new message is added that can have three replies?

Another option would be to add a cec_msg flag, but really, the combination
of CEC_MSG_REPORT_ARC_INITIATED and a reply value of one of the two
possible replies already functions as a flag.

Another advantage of this approach is that it is safe to re-use a
cec_msg struct. No need to zero a flags field or a reply2 field.

So since this really is an exception in the CEC specification, I
decided to implement it as an exception as well.

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent 3074fe4a

Documentation/media/uapi/cec/cec-ioc-receive.rst

+8 −0
Original line number Diff line number Diff line
@@ -142,6 +142,14 @@ result. 
	Feature Abort reply. In this case ``rx_status`` will either be set

	to :ref:`CEC_RX_STATUS_TIMEOUT <CEC-RX-STATUS-TIMEOUT>` or

	:ref:`CEC_RX_STATUS_FEATURE_ABORT <CEC-RX-STATUS-FEATURE-ABORT>`.



	If the transmitter message is ``CEC_MSG_INITIATE_ARC`` then the ``reply``

	values ``CEC_MSG_REPORT_ARC_INITIATED`` and ``CEC_MSG_REPORT_ARC_TERMINATED``

	are processed differently: either value will match both possible replies.

	The reason is that the ``CEC_MSG_INITIATE_ARC`` message is the only CEC

	message that has two possible replies other than Feature Abort. The

	``reply`` field will be updated with the actual reply so that it is

	synchronized with the contents of the received message.

    * - __u8

      - ``rx_status``

      - The status bits of the received message. See

drivers/staging/media/cec/TODO

+1 −14
Original line number Diff line number Diff line 
The reason why cec.c is still in staging is that I would like

to have a bit more confidence in the uABI. The kABI is fine,

no problem there, but I would like to let the public API mature

a bit.

TODOs:



Once I'm confident that I didn't miss anything then the cec.c source

can move to drivers/media and the linux/cec.h and linux/cec-funcs.h

headers can move to uapi/linux and added to uapi/linux/Kbuild to make

them public.



Hopefully this will happen later in 2016.



Other TODOs:



- There are two possible replies to CEC_MSG_INITIATE_ARC. How to handle that?

- Should CEC_LOG_ADDR_TYPE_SPECIFIC be replaced by TYPE_2ND_TV and TYPE_PROCESSOR?

  And also TYPE_SWITCH and TYPE_CDC_ONLY in addition to the TYPE_UNREGISTERED?

  This should give the framework more information about the device type

drivers/staging/media/cec/cec-adap.c

+12 −0
Original line number Diff line number Diff line
@@ -958,6 +958,18 @@ void cec_received_msg(struct cec_adapter *adap, struct cec_msg *msg) 
		list_for_each_entry(data, &adap->wait_queue, list) {

			struct cec_msg *dst = &data->msg;



			/*

			 * The *only* CEC message that has two possible replies

			 * is CEC_MSG_INITIATE_ARC.

			 * In this case allow either of the two replies.

			 */

			if (!abort && dst->msg[1] == CEC_MSG_INITIATE_ARC &&

			    (cmd == CEC_MSG_REPORT_ARC_INITIATED ||

			     cmd == CEC_MSG_REPORT_ARC_TERMINATED) &&

			    (dst->reply == CEC_MSG_REPORT_ARC_INITIATED ||

			     dst->reply == CEC_MSG_REPORT_ARC_TERMINATED))

				dst->reply = cmd;



			/* Does the command match? */

			if ((abort && cmd != dst->msg[1]) ||

			    (!abort && cmd != dst->reply))