From: Adam Jackson <ajax@redhat.com>
To: Gerd Hoffmann <kraxel@redhat.com>, dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>,
open list <linux-kernel@vger.kernel.org>,
"open list:DRM DRIVER FOR QEMU'S CIRRUS DEVICE"
<virtualization@lists.linux-foundation.org>,
Dave Airlie <airlied@redhat.com>
Subject: Re: [PATCH] drm/cirrus: rewrite and modernize driver.
Date: Wed, 03 Apr 2019 11:12:05 -0400 [thread overview]
Message-ID: <85ba308177f4e9ddee336d5110cb6df7a447cebf.camel@redhat.com> (raw)
In-Reply-To: <20190403072318.31507-1-kraxel@redhat.com>
On Wed, 2019-04-03 at 09:23 +0200, Gerd Hoffmann wrote:
> - Only DRM_FORMAT_RGB565 (depth 16) is supported. The old driver does
> that too by default. There was a module parameter which enables 24/32
> bpp support and disables higher resolutions (due to cirrus hardware
> constrains). That parameter wasn't reimplemented.
One slightly annoying aspect of this (well, initially of the patch to
clamp the default to 16bpp, but this too) is that we only have a way to
ask the driver which format it prefers, not which ones it supports at
all. For X's modesetting driver (and yes some of this is because X is
awful) this creates the following failure mode:
1: user sets up xorg.conf for depth 24
2: user upgrades kernel, reboots
3: X driver detects that depth 16 is preferred, but
4: X core respects user's xorg.conf and tries depth 24, which
5: throws -EINVAL and X won't start.
Possibly X should work around this by transparently setting up a shadow
framebuffer at the user's requested depth. The problem there is, if 565
is preferred but 8888 works, you're adding a format-conversion blit in
the middle for no reason. If I could ask the kernel for the entire list
of supported formats, I could only set up the shadow if it was
necessary.
- ajax
next prev parent reply other threads:[~2019-04-03 15:12 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-03 7:23 [PATCH] drm/cirrus: rewrite and modernize driver Gerd Hoffmann
2019-04-03 7:47 ` Daniel Vetter
2019-04-03 8:53 ` Gerd Hoffmann
2019-04-03 9:58 ` Noralf Trønnes
2019-04-03 10:27 ` Gerd Hoffmann
2019-04-03 15:12 ` Adam Jackson [this message]
2019-04-03 15:15 ` Daniel Stone
2019-04-03 15:52 ` Adam Jackson
2019-04-04 2:58 ` David Airlie
2019-04-04 5:50 ` Gerd Hoffmann
2019-04-04 6:31 ` Daniel Vetter
2019-04-04 7:09 ` Gerd Hoffmann
2019-04-04 8:30 ` Gerd Hoffmann
2019-04-04 8:52 ` Daniel Vetter
2019-04-04 10:06 ` Noralf Trønnes
2019-04-04 10:27 ` Gerd Hoffmann
2019-04-04 11:45 ` Noralf Trønnes
2019-04-04 11:45 ` Gerd Hoffmann
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