Re: [PATCH 7/7] drm/fb-helper: Don't use the preferred depth for the BPP default

[Javier Martinez Canillas <javierm@redhat.com>]

On 11/16/22 17:09, Thomas Zimmermann wrote:
> If no preferred value for bits-per-pixel has been given, fall back
> to 32. Never use the preferred depth. The color depth is the number
> of color/alpha bits per pixel, while bpp is the overall number of
> bits in most cases.
> 
> Most noteworthy, XRGB8888 has a depth of 24 and a bpp value of 32.
> Using depth for bpp would make the value 24 as well and format
> selection in fbdev helpers fails. Unfortunately XRGB8888 is the most
> common format and the old heuristic therefore fails for most of
> the drivers (unless they implement the 24-bit RGB888 format).
> 
> Picking a bpp of 32 will lateron result in a default depth of 24

later on

> and the format XRGB8888. As XRGB8888 is the default format for most
> of the current and legacy graphics stack, all drivers must support
> it. So it is the safe choice.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---

Agreed that 32 is a safe choice in this case.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat