Den 16.12.2021 09.20, skrev Thomas Zimmermann:
Hi
Am 15.12.21 um 22:37 schrieb Noralf Trønnes:
Den 15.12.2021 01.59, skrev Javier Martinez Canillas:
According to disable Documentation/admin-guide/kernel-parameters.txt, this parameter can be used to disable kernel modesetting.
DRM drivers will not perform display-mode changes or accelerated rendering and only the systewm system framebuffer will be available if it was set-up.
But only a few DRM drivers currently check for nomodeset, make this driver to also support the command line parameter.
Signed-off-by: Javier Martinez Canillas javierm@redhat.com
I don't understand why this is applicable to USB drivers, there's no way the firmware can setup a framebuffer and continue pushing pixels over USB when Linux has been given control over the USB bus?
The same argument goes for the SPI drivers in drm/tiny/ as well.
The intended semantics of the option is to disable every display output except for the buffer provided by the firmware.
If that's the case this patch is:
Acked-by: Noralf Trønnes noralf@tronnes.org
With USB it still would still disable the driver. That's useful if only for debugging. There are also systems with hard-wired USB displays where one cannot just unplug the adapter.
Admittedly, USB graphics is a bit of an odd use case, but neither is it too far fetched IMHO.
Best regards Thomas
Noralf.
drivers/gpu/drm/gud/gud_drv.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/gud/gud_drv.c b/drivers/gpu/drm/gud/gud_drv.c index 3f9d4b9a1e3d..4d253d249512 100644 --- a/drivers/gpu/drm/gud/gud_drv.c +++ b/drivers/gpu/drm/gud/gud_drv.c @@ -446,6 +446,9 @@ static int gud_probe(struct usb_interface *intf, const struct usb_device_id *id) u32 *formats; int ret, i; + if (drm_firmware_drivers_only()) + return -ENODEV;
ret = usb_find_bulk_out_endpoint(intf->cur_altsetting, &bulk_out); if (ret) return ret;