From: Maxime Ripard <mripard@kernel.org>
To: Francesco Valla <francesco@valla.it>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@gmail.com>,
Simona Vetter <simona@ffwll.ch>,
Jonathan Corbet <corbet@lwn.net>,
Jocelyn Falempe <jfalempe@redhat.com>,
Javier Martinez Canillas <javierm@redhat.com>,
Sam Ravnborg <sam@ravnborg.org>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-doc@vger.kernel.org, linux-embedded@vger.kernel.org
Subject: Re: [PATCH RFC 0/3] Add splash DRM client
Date: Mon, 27 Oct 2025 11:09:56 +0100 [thread overview]
Message-ID: <yq4btdc5qqukuqps7y53dratmu64ghyifgprlndnk5rbgml4of@rvca75sncvsm> (raw)
In-Reply-To: <20251027-drm_client_splash-v1-0-00698933b34a@valla.it>
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Hi,
On Mon, Oct 27, 2025 at 12:03:00AM +0100, Francesco Valla wrote:
> this patchset adds a new DRM client offering splash functionalities,
> able to draw to screen:
>
> - a colored background;
So, I like that part, and we were recently discussing about this.
> - a single-line text message, which can be set through sysfs or
> directly from the kernel command line;
> - a very simple progress bar, which can be driven through sysfs;
> - a static image (optional).
But there's no reason to have all that in the kernel, and we already
have userspace components to do so (plymouth being the main "mainstream"
one).
> Once compiled inside the kernel, the client can be enabled through the
> command line specifying the drm_client_lib.active=splash parameter.
>
> == Motivation ==
>
> The motivation behind this work is to offer to embedded system
> developers a new path for a simple activation of the display(s)
> connected to their system, with the following usecases:
>
> - bootsplash - possibly displaying even before init;
> - early activation of the display pipeline, in particular whenever one
> component of the pipeline (e.g.: a panel) takes a non-negligible
> time to initialize;
> - recovery systems, where the splash client can offer a simple feedback
> for unattended recovery tasks;
> - update systems, where the splash client can offer a simple feedback
> for unattended update tasks.
If plymouth cannot be used by embedded systems for some reason, then you
should work on a plymouth alternative.
> While the first seems the most obvious one, it was the second that acted
> as the driver, as in the past I had to implement a ugly workaround using
> a systemd generator to kickstart the initialization of a display and
> shave ~400ms of boot time.
>
> The last 2 usecase, instead, are the reason I dropped the "boot" part
> from bootsplash.
>
> == Implementation details ==
>
> The design is quite simple, with a kernel thread doing the heavylifting
> for the rendering part and some locking to protect interactions with it.
>
> The splash image is loaded using the firmware framework, with the client
> expecting to find a binary dump having the right dimensions (width and
> height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
> modeset, the client will for example search for a firmware named:
>
> drm_splash_1920x1080_RG24.raw
>
> If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
> mechanism is used to let userspace load the appropriate image.
>
> == Testing ==
>
> Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
> display connected to a Beagleplay and on a ILI9341 SPI display connected
> to a i.MX93 FRDM board. All these platforms revealed different
> weaknesses that were hopefully removed.
>
> == Open points / issues ==
>
> The reason for this being an RFC is that there are several open points:
>
> - Support for tiled connectors should be there, but has not been
> tested. Any idea on how to test it?
Did you mean tiled formats?
> - I'm not entirely convinced that using the firmware framework to load
> the images is the right path. The idea behind it was to re-use the
> compressed firmware support, but then I discovered it is not there
> for built-in firmware.
Yeah, firmware loading for this has a few issues (being tedious to setup
for when built-in being one). I think just going the fbdev penguin road
is a better choice: you provide the path, and it's embedded in the
kernel directly.
> - Again on the firmware loading: CONFIG_LOADPIN would interfere with
> sysfs loading.
> - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
> leading me to think it is de-facto deprecated. And still, uevents
> for firmware loading seem frowned upon these days...
> - Generating binary dumps for... basically any format is not so
> straightforward. I crafted a Python tool with AI help which seems
> to work quite well, but I honestly did not yet understood which is
> the policy for AI-generated code inside the kernel, so it is not
> included in this patch set. All client code is genuine, though.
BMP is simple enough to support so we should probably use that instead
of a custom format.
Maxime
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next prev parent reply other threads:[~2025-10-27 10:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-26 23:03 [PATCH RFC 0/3] Add splash DRM client Francesco Valla
2025-10-26 23:03 ` [PATCH RFC 1/3] drm: client: add splash client Francesco Valla
2025-10-26 23:03 ` [PATCH RFC 2/3] MAINTAINERS: add entry for DRM " Francesco Valla
2025-10-26 23:03 ` [PATCH RFC 3/3] drm: docs: remove bootsplash from TODO Francesco Valla
2025-10-27 10:09 ` Maxime Ripard [this message]
2025-10-27 12:35 ` [PATCH RFC 0/3] Add splash DRM client Thomas Zimmermann
2025-10-27 16:01 ` Mario Limonciello
2025-10-27 16:28 ` Maxime Ripard
2025-10-27 16:31 ` Mario Limonciello
2025-10-27 17:19 ` Maxime Ripard
2025-10-28 8:09 ` Francesco Valla
2025-10-28 13:39 ` Mario Limonciello
2025-10-29 8:36 ` Maxime Ripard
2025-10-28 8:03 ` Francesco Valla
2025-10-28 7:58 ` Francesco Valla
2025-10-29 8:34 ` Maxime Ripard
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