Re: [PATCH v2 1/2] drm: Add a drm_drv_enabled() to check if drivers should be enabled

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 04.11.21 um 21:09 schrieb Javier Martinez Canillas:
> Hello Jani,
> 
> On 11/4/21 20:57, Jani Nikula wrote:
>> On Thu, 04 Nov 2021, Javier Martinez Canillas <javierm@redhat.com> wrote:
>>> +/**
>>> + * drm_drv_enabled - Checks if a DRM driver can be enabled
>>> + * @driver: DRM driver to check
>>> + *
>>> + * Checks whether a DRM driver can be enabled or not. This may be the case
>>> + * if the "nomodeset" kernel command line parameter is used.
>>> + *
>>> + * Return: 0 on success or a negative error code on failure.
>>> + */
>>> +int drm_drv_enabled(const struct drm_driver *driver)

Jani mentioned that i915 absolutely wants this to run from the 
module_init function. Best is to drop the parameter.

>>> +{
>>> +	if (vgacon_text_force()) {
>>> +		DRM_INFO("%s driver is disabled\n", driver->name);
>>> +		return -ENODEV;
>>> +	}

If we run this from within a module_init function, we'd get plenty of 
these warnings if drivers are compiled into the kernel. Maybe simply 
remove the message. There's already a warning printed by the nomodeset 
handler.

>>> +
>>> +	return 0;
>>> +}
>>> +EXPORT_SYMBOL(drm_drv_enabled);
>>
>> The name implies a bool return, but it's not.
>>
>> 	if (drm_drv_enabled(...)) {
>> 		/* surprise, it's disabled! */
>> 	}
>>
> 
> It used to return a bool in v2 but Thomas suggested an int instead to
> have consistency on the errno code that was returned by the callers.
> 
> I should probably name that function differently to avoid confusion.

Yes, please.

Best regards
Thomas

> 
> But I think you are correct and this change is caused too much churn
> for not that much benefit, specially since is unclear that there might
> be another condition to prevent a DRM driver to load besides nomodeset.
> 
> I'll just drop this patch and post only #2 but making drivers to test
> using the drm_check_modeset() function (which doesn't have a name that
> implies a bool return).
> 
>>
>> BR,
>> Jani.
>>
>>
>>
> 
> Best regards,
> 

-- 
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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