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

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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@xxxxxxxxxx> 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;

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

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).


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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