linux-kernel - Re: [PATCH 11/60] drm/gud: Add support for the nomodeset kernel parameter

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Message-ID: <55881b86-6130-7737-b6f8-44e1853e419a@redhat.com>
Date:   Wed, 15 Dec 2021 22:50:40 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Noralf Trønnes <noralf@...nnes.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 11/60] drm/gud: Add support for the nomodeset kernel
 parameter

Hello Noralf,

On 12/15/21 22:37, Noralf Trønnes wrote:
> 
> 
> Den 15.12.2021 01.59, skrev Javier Martinez Canillas:
>> According to disable Documentation/admin-guide/kernel-parameters.txt, this
>> parameter can be used to disable kernel modesetting.
>>
>> DRM drivers will not perform display-mode changes or accelerated rendering
>> and only the systewm system framebuffer will be available if it was set-up.
>>
>> But only a few DRM drivers currently check for nomodeset, make this driver
>> to also support the command line parameter.
>>
>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>> ---
>>
> 
> I don't understand why this is applicable to USB drivers, there's no way
> the firmware can setup a framebuffer and continue pushing pixels over
> USB when Linux has been given control over the USB bus?
> 
> The same argument goes for the SPI drivers in drm/tiny/ as well.
> 

That's a very good point. I included these mostly for consistency but if it's
OK for the KMS drivers to just ignore the "nomodeset" parameter, I could drop
all that are not for devices in the PCI or platform buses.

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat