linux-kernel - Re: [PATCH 1/3] media: venus: Add support for static video encoder/decoder declarations

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Message-ID: <95ec73c9-da38-4888-9e00-4458b5a7661c@linaro.org>
Date: Thu, 28 Nov 2024 22:14:16 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
 Vikash Garodia <quic_vgarodia@...cinc.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: quic_renjiang@...cinc.com, quic_vnagar@...cinc.com,
 quic_dikshita@...cinc.com, konradybcio@...nel.org,
 linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Stanimir Varbanov <stanimir.varbanov@...aro.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/3] media: venus: Add support for static video
 encoder/decoder declarations

On 28/11/2024 20:02, Konrad Dybcio wrote:
> On 27.11.2024 2:34 AM, Bryan O'Donoghue wrote:
>> Add resource structure data and probe() logic to support static
>> declarations of encoder and decoder.
>>
>> Right now we rely on video encoder/decoder selection happening in the dtb
>> but, this goes against the remit of device tree which is supposed to
>> describe hardware, not select functional logic in Linux drivers.
>>
>> Provide two strings in the venus resource structure enc_nodename and
>> dec_nodename.
>>
>> When set the venus driver will create an OF entry in-memory consistent
>> with:
>>
>> dec_nodename {
>>      compat = "video-decoder";
>> };
>>
>> and/or
>>
>> enc_nodename {
>>      compat = "video-encoder";
>> };
>>
>> This will allow us to reuse the existing driver scheme of relying on compat
>> names maintaining compatibility with old dtb files.
>>
>> dec_nodename can be "video-decoder" or "video0"
>> enc_nodename can be "video-encoder" or "video1"
>>
>> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>> ---
> 
> Bryan,
> 
> I'm still not sure if keeping the logic behind this makes sense at all.
> 
> Could we not just call platform_device_register_data() with a static
> configuration of 1 core being enc and the other dec?

That's another way to do this. One reason I wrote this series to 
continue to rely on the existing compat= method though is it stuck in my 
mind that we have some dependency ordering logic in at the moment.

For example:

commit 08b1cf474b7f72750adebe0f0a35f8e9a3eb75f6
Author: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Date:   Fri Feb 5 19:11:49 2021 +0100

And the other reason is the prototype platform_device_register_* looks 
like more surgery and ultimately more validation / potential for bugs.

Since this driver is supposed to be moving to maintenance mode, I didn't 
want to do a more major rewrite of the probe() and remove() paths.

---
bod