[PATCH] drm/vkms: Unset preferred_depth

[Thomas Zimmermann]

Hi

On 20.10.20 10:35, Daniel Vetter wrote:
> There's a confusion between the preferred_depth uapi and the generic
> fbdev helpers. Former wants depth, latter wants bpp, and for XRGB8888
> they don't match. Which hit me with vkms, which wants that.
> 
> All other drivers setting this and using the generic fbdev helpers use
> 16, where both numbers match, for RGB565.
> 
> Since fixing this is a bit involved (I think for atomic drivers we
> should just compute this all internally from the format list of the
> first primary plane) paper over the issue in vkms by using defaults
> everywhere. Then userspace will pick XRGB8888, and fbdev helpers will
> do the same, and we have what we want.
> 
> Reported-by: Simon Ser <contact at emersion.fr>
> Cc: Simon Ser <contact at emersion.fr>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Rodrigo Siqueira <rodrigosiqueiramelo at gmail.com>
> Cc: Melissa Wen <melissa.srw at gmail.com>
> Cc: Haneen Mohammed <hamohammed.sa at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> ---
>  drivers/gpu/drm/vkms/vkms_drv.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 25faba5aac08..98ba844ae77d 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -114,7 +114,10 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
>  	dev->mode_config.max_height = YRES_MAX;
>  	dev->mode_config.cursor_width = 512;
>  	dev->mode_config.cursor_height = 512;
> -	dev->mode_config.preferred_depth = 32;
> +	/* FIXME: There's a confusion between bpp and depth between this and
> +	 * fbdev helpers. We have to go with 0, meaning "pick the default",
> +	 * which ix XRGB8888 in all cases. */
> +	dev->mode_config.preferred_depth = 0;

It's already 0 at this point.

I suggest to rather document this FIXME as part of the documentation of
drm_fbdev_generic_setup() and preferred_depth. Other drivers are also
affected.

Best regards
Thomas

>  	dev->mode_config.helper_private = &vkms_mode_config_helpers;
>  
>  	return vkms_output_init(vkmsdev, 0);
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer