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

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Date:   Thu, 28 Mar 2019 17:33:31 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Reza Arbab <arbab@...ux.ibm.com>
Cc:     Dave Airlie <airlied@...hat.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Robert Tarasov <tutankhamen@...omium.org>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        wzabolot@...ktron.elka.pw.edu.pl, Pavel Machek <pavel@....cz>,
        Alex Deucher <alexander.deucher@....com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>
Subject: Re: [PATCH 2/2] drm/fb-helper: Do not scale depth down to 0

On Fri, Mar 22, 2019 at 9:56 PM Reza Arbab <arbab@...ux.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@...ux.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