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Subject: Re: [PATCH v7 1/3] media: cec: expose HDMI connector to CEC dev
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From:   Hans Verkuil <hverkuil@xs4all.nl>
To:     Dariusz Marcinkiewicz <darekm@google.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190521105203.154043-1-darekm@google.com>
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Message-ID: <a421ff13-c8ee-b72c-3e1e-376b9e426064@xs4all.nl>
Date:   Wed, 29 May 2019 16:47:42 +0200
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On 5/28/19 10:05 AM, Hans Verkuil wrote:
> On 5/28/19 9:53 AM, Dariusz Marcinkiewicz wrote:
>> On Fri, May 24, 2019 at 11:21 AM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>>>
>>> Hi Dariusz,
>>>
>>> I did some more testing with the Khadas VIM2 and found another problem,
>>> something that will, unfortunately, require some redesign.
>>>
>> ...
>>>
>>> The other problem is in the CEC driver: it creates the CEC device as
>>> soon as the HDMI device is found (cec_notifier_parse_hdmi_phandle).
>>>
>>> But that doesn't mean that the HDMI device also had registered itself
>>> as a CEC notifier.
>>>
>>> Until now that never mattered: as long as the HDMI device was found
>>> the CEC adapter would function fine, it would just have no physical
>>> address until so notified by the HDMI device once it registered its
>>> CEC notifier.
>>>
>>> But if we want to have valid connector info during the lifetime of
>>> the CEC adapter, then this no longer works.
>>>
>>> I'm not entirely sure how to handle this.
>>>
>>> Another issue here is that when the HDMI driver removes the notifier,
>>> then it should also zero the connector info. Remember that both the
>>> HDMI and the CEC drivers can be loaded and unloaded independently from
>>> one another.
>>>
>> Given all of the above, what do you think about coming back to the v1
>> of the patch, where a connector info could be set on an adapter at any
>> time and an event was used to notify userland when that happened? That
>> approach seems to cover all the scenarios mentioned above.
> 
> That's just hiding the real problems :-)
> 
> I hope to spend some time on CEC tomorrow and I'll get back to you then.

Unfortunately I had too many other things going on to spend time on this.

Hopefully next week.

Regards,

	Hans