Re: [PATCH] drm/xe: Support 'nomodeset' kernel command-line option

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 21.08.24 um 16:16 schrieb Gustavo Sousa:
> Quoting Thomas Zimmermann (2024-08-21 10:56:59-03:00)
>> Setting 'nomodeset' on the kernel command line disables all graphics
>> drivers with modesetting capabilities; leaving only firmware drivers,
>> such as simpledrm or efifb.
>>
>> Most DRM drivers automatically support 'nomodeset' via DRM's module
>> helper macros. In xe, which uses regular module_init(), manually call
>> drm_firmware_drivers_only() to test for 'nomodeset'. Do not register
>> the driver if set.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>> drivers/gpu/drm/xe/xe_module.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_module.c b/drivers/gpu/drm/xe/xe_module.c
>> index 923460119cec..60fb7dd26903 100644
>> --- a/drivers/gpu/drm/xe/xe_module.c
>> +++ b/drivers/gpu/drm/xe/xe_module.c
>> @@ -8,6 +8,8 @@
>> #include <linux/init.h>
>> #include <linux/module.h>
>>
>> +#include <drm/drm_module.h>
>> +
>> #include "xe_drv.h"
>> #include "xe_hw_fence.h"
>> #include "xe_pci.h"
>> @@ -92,6 +94,9 @@ static int __init xe_init(void)
>> {
>>          int err, i;
>>
>> +        if (drm_firmware_drivers_only())
>> +                return -ENODEV;
>> +
> Hm... But what if xe is to be used only for compute or render? Shouldn't
> we handle this somewhere else?

The semantics of 'nomodeset' is a bit vague in this case. The option is 
supposed to disable all of the driver in case there's a significant 
problem with booting up. Other drivers do that. And users should be able 
to specify 'nomodeset' and reliably get some display output; whether the 
problem is in KMS or rendering.

I suggest to stick with that behavior, even if that disables other 
functionality as well. Up to you.

Best regards
Thomas

>
> Taking a quick look, xe_display_probe() might be a good candidate?
>
> --
> Gustavo Sousa
>
>>          for (i = 0; i < ARRAY_SIZE(init_funcs); i++) {
>>                  err = init_funcs[i].init();
>>                  if (err) {
>> -- 
>> 2.46.0
>>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)