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. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
