On Fri, Aug 12, 2016 at 05:53:17PM +0200, Hans Verkuil wrote:

There are three possible 'states' of a CEC adapter w.r.t. logical addresses:

1) There is no physical address or no logical addresses have been set
by the application (CEC_ADAP_S_LOG_ADDRS): in that case the device
will not participate on the bus, it doesn't care about receiving messages
let alone replying to them. The only exception is if the device can
snoop messages, that is allowed even if CEC_ADAP_S_LOG_ADDRS is never
called. That is ideal to have a 'neutral' observer of the bus that just
listens but never participates. Not all hardware supports snooping, though.

2) CEC_ADAP_S_LOG_ADDRS is called and the device becomes an 'Unregistered'
device (i.e. it gets logical address 15). In that case it should receive
broadcast messages and be able to transmit messages.

3) CEC_ADAP_S_LOG_ADDRS is called and the device claims one or more logical
addresses in the range 0-14. Then it can receive broadcast and directed
messages, and of course transmit messages.

From the point of view of the hardware state 1 is selected if adap_log_addr
is called with LOG_ADDR_INVALID. Some hardware might still receive broadcast
messages (because they can't turn that off) and those should be filtered out
by the CEC framework. But I think that doesn't happen, which would be a bug.
I'll verify that tomorrow.

State 2 is a problem for hardware that has to enable support to receive
broadcast messages since adap_log_addr is never called with
LOG_ADDR_UNREGISTERED as argument. I missed that, since the hardware I tested
with always accepts broadcast messages. I'll look into this tomorrow as well.
It should be easy to fix.

State 3 works OK.

So for the dw-hdmi cec driver that means that for state 1 you set 'addresses'
to 0, for state 2 you set it to BIT(15) and for state 3 you always
OR with BIT(15). At least, as I understand your hardware.

Thanks, I think that needs documenting in Documentation/cec.txt.

BTW, if either the tda or dw-hdmi supports snooping mode, then I strongly
recommend supporting that. It's great for debugging.

Neither do.

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