[PATCH 2/2] drm/fb-helper: Do not scale depth down to 0

[Linus Walleij]

On Fri, Mar 22, 2019 at 9:56 PM Reza Arbab <arbab at linux.ibm.com> wrote:

> If the scaling loop in drm_fb_helper_single_fb_probe() only finds
> supported depths greater than what it's looking for, it will set
> sizes.surface_depth = 0. This broke my udl device:
>
> [drm] test CRTC 0 primary plane
> udl 3-9.1:1.0: drm_fb_helper_single_fb_probe: test CRTC 0 format 0, depth=24
> udl 3-9.1:1.0: drm_fb_helper_single_fb_probe: 24 > 16, skipping
> udl 3-9.1:1.0: drm_fb_helper_single_fb_probe: test CRTC 0 format 1, depth=32
> udl 3-9.1:1.0: drm_fb_helper_single_fb_probe: 32 > 16, skipping
> [drm] requested bpp 16, scaled depth down to 0
>
> Instead of setting zero depth, print that scaling was not possible and
> do nothing.
>
> Fixes: f4bd542bcaee ("drm/fb-helper: Scale back depth to supported maximum")
> Signed-off-by: Reza Arbab <arbab at linux.ibm.com>

This makes perfect sense, but Dave Airlie already sent a similar
patch some two weeks ago, I wonder what happened with it?
Subject "avoid setting 0 depth".

Yours,
Linus Walleij