linux-kernel - Re: [PATCH 3/3] drm/panic: Add a kconfig option to dump kunits results to png

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Message-ID: <pucvcimuuyz7f7ih7hx7l6bmutarlryvzwiqh7a26bk65ya5sf@uj7agoqm4lm3>
Date: Tue, 2 Sep 2025 18:58:00 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Jocelyn Falempe <jfalempe@...hat.com>
Cc: Thomas Zimmermann <tzimmermann@...e.de>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Javier Martinez Canillas <javierm@...hat.com>, 
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 3/3] drm/panic: Add a kconfig option to dump kunits
 results to png

On Mon, Sep 01, 2025 at 03:04:26PM +0200, Jocelyn Falempe wrote:
> On 27/08/2025 12:45, Thomas Zimmermann wrote:
> > Hi
> > 
> > Am 21.08.25 um 11:49 schrieb Jocelyn Falempe:
> > > This is a bit hacky, but very handy if you want to customize the
> > > panic screen.
> > > It allows to dump the generated images to the logs, and then a python
> > > script can convert it to .png files. It makes it easy to check how
> > > the panic screen will look on different resolutions, without having
> > > to crash a VM.
> > > To not pollute the logs, it uses a monochrome framebuffer, compress
> > > it with zlib, and base64 encode it.
> > 
> > May I suggest to export the raw image via debugfs? Debugfs can also
> > export additional information in additional files, such as width/height/
> > stride/format. This could provide the real/last image on the fly, simply
> > by reading the files. No workarounds or encodings needed.
> 
> I'm looking into that. The difficulty is to get the debugfs content outside
> of the test kernel. As I'm using a uml kernel for testing, I will need a
> special initrd, and a way to share files with the host.

Yeah, I agree that it's not very practical. If only because the test
context doesn't stick around once it's been executed, so you would
effectively leak an arbritrarily long buffer with no hope of getting
back its memory.

Maxime

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