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

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Date:   Wed, 19 Jun 2019 13:05:11 +0200
From:   Dariusz Marcinkiewicz <darekm@...gle.com>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     linux-media@...r.kernel.org, hans.verkuil@...co.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/3] media: cec: expose HDMI connector to CEC dev mapping

Hi Hans.

I would like to come back to this thread.

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.
>
> See my comments below...
>
...
>
> 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.
>

I took a peek at the changes in
https://git.linuxtv.org/hverkuil/media_tree.git/log/?h=cec-conn. Do I
understand it correctly, that the above problem is addressed there by
unregistering an adapter in cec_notifier_conn_unregister (which will
result in /dev/cecX node going away)? I wonder to what degree this
solves the problem of HDMI and CEC drivers being loaded and unloaded
independently. It seems that in cases where HDMI driver is unloaded
and then loaded again, counterintuitively, the /dev/cecX might not
come back again, is this right, or am I missing something? Also, is it
guaranteed that adapter drivers won't try to access an adapter once it
gets removed by cec_notifier_conn_unregister?

Thank you.