Re: [PATCH 1/2] drm: Move nomodeset kernel parameter to drivers/video

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 11.11.22 um 10:28 schrieb Javier Martinez Canillas:
> Hello Thomas,
> 
> On 11/7/22 11:49, Thomas Zimmermann wrote:
> 
> [...]
> 
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index a465d5242774a..70178c5f53956 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -3777,7 +3777,7 @@
>>   			shutdown the other cpus.  Instead use the REBOOT_VECTOR
>>   			irq.
>>   
>> -	nomodeset	Disable kernel modesetting. DRM drivers will not perform
>> +	nomodeset	Disable kernel modesetting. Graphics drivers will not perform
>>   			display-mode changes or accelerated rendering. Only the
>>   			system framebuffer will be available for use if this was
>>   			set-up by the firmware or boot loader.
> 
> Not really part of your patch but probably we should reword this a little bit.
> 
> Because as this is written, it implies that not only DRM drivers with feature
> DRIVER_MODESET will not be available but also drivers with DRIVER_RENDER. But
> that's not the case, render-only drivers usually just ignore this parameter
> (but not all IIRC), so I wonder how we could make this comment more accurate.

I see what you mean, but it's hard to describe in simple words. The 
option is a bit fuzzy. It means that a driver will not replace a 
firmware buffer; even if that means it won't initialize at all. I guess 
we should spell that out.

> 
> Also maybe we can mention in the comment fbdev and DRM? Just to make it clear
> that this will affect to both subsystems? When I first worked on this, there
> were a lot of assumptions in the stack (gdm, mutter, plymouth) that nomodeset
> basically meant "no DRM but fbdev".

I can change the text to say 'DRM and fbdev drivers'.

Best regards
Thomas

> 
> [...]
> 
>>   
>>   int drm_dev_set_unique(struct drm_device *dev, const char *name);
>>   
>> -extern bool drm_firmware_drivers_only(void);
>> +/* TODO: Inline drm_firmware_drivers_only() in all its callers. */
> 
> I guess you plan to do that as follow-up patches once this series land? Just
> to avoid the churn to require acks for all the drivers to merge this series?
> 
> The changes looks good to me.
> 
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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