linux-kernel - Re: [PATCH v7 1/3] media: cec: expose HDMI connector to CEC dev mapping

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Date:   Tue, 28 May 2019 10:05:47 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Dariusz Marcinkiewicz <darekm@...gle.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/3] media: cec: expose HDMI connector to CEC dev
 mapping

On 5/28/19 9:53 AM, Dariusz Marcinkiewicz wrote:
> On Fri, May 24, 2019 at 11:21 AM Hans Verkuil <hverkuil@...all.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.

Regards,

	Hans