On Thu, 04 Nov 2021, Sam Ravnborg <sam@xxxxxxxxxxxx> wrote:
> Hi Javier,
>
> On Thu, Nov 04, 2021 at 05:07:06PM +0100, Javier Martinez Canillas wrote:
>> Some DRM drivers check the vgacon_text_force() function return value as an
>> indication on whether they should be allowed to be enabled or not.
>>
>> This function returns true if the nomodeset kernel command line parameter
>> was set. But there may be other conditions besides this to determine if a
>> driver should be enabled.
>>
>> Let's add a drm_drv_enabled() helper function to encapsulate that logic so
>> can be later extended if needed, without having to modify all the drivers.
>>
>> Also, while being there do some cleanup. The vgacon_text_force() function
>> is guarded by CONFIG_VGA_CONSOLE and there's no need for callers to do it.
>>
>> Suggested-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
>> Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
>> ---
>>
>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>> index 8214a0b1ab7f..3fb567d62881 100644
>> --- a/drivers/gpu/drm/drm_drv.c
>> +++ b/drivers/gpu/drm/drm_drv.c
>> @@ -975,6 +975,26 @@ int drm_dev_set_unique(struct drm_device *dev, const char *name)
>> }
>> EXPORT_SYMBOL(drm_dev_set_unique);
>>
>> +/**
>> + * 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)
>> +{
>> + if (vgacon_text_force()) {
>> + DRM_INFO("%s driver is disabled\n", driver->name);
>
> DRM_INFO is deprecated, please do not use it in new code.
> Also other users had an error message and not just info - is info
> enough?
>
>
>> + return -ENODEV;
>> + }
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL(drm_drv_enabled);
>> +
>> /*
>> * DRM Core
>> * The DRM core module initializes all global DRM objects and makes them
>> diff --git a/drivers/gpu/drm/i915/i915_module.c b/drivers/gpu/drm/i915/i915_module.c
>> index ab2295dd4500..45cb3e540eff 100644
>> --- a/drivers/gpu/drm/i915/i915_module.c
>> +++ b/drivers/gpu/drm/i915/i915_module.c
>> @@ -18,9 +18,12 @@
>> #include "i915_selftest.h"
>> #include "i915_vma.h"
>>
>> +static const struct drm_driver driver;
> Hmmm...
>
>> +
>> static int i915_check_nomodeset(void)
>> {
>> bool use_kms = true;
>> + int ret;
>>
>> /*
>> * Enable KMS by default, unless explicitly overriden by
>> @@ -31,7 +34,8 @@ static int i915_check_nomodeset(void)
>> if (i915_modparams.modeset == 0)
>> use_kms = false;
>>
>> - if (vgacon_text_force() && i915_modparams.modeset == -1)
>> + ret = drm_drv_enabled(&driver);
>
> You pass the local driver variable here - which looks wrong as this is
> not the same as the driver variable declared in another file.
Indeed.
> Maybe move the check to new function you can add to init_funcs,
> and locate the new function in i915_drv - so it has access to driver?
We don't really want that, though. This check is pretty much as early as
it can be, and there's a ton of useless initialization that would happen
if we waited until drm_driver is available.
>From my POV, drm_drv_enabled() is a solution that creates a worse
problem for us than it solves.
BR,
Jani.
>
>
> Sam
--
Jani Nikula, Intel Open Source Graphics Center