linux-kernel - Re: [PATCH RFC v2 1/3] drm: client: add splash client

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Message-ID: <CAMuHMdUtsx1gQffk9c-U9UkeqG_Dopv5vXNrp72ewh0EQQgwjQ@mail.gmail.com>
Date: Tue, 6 Jan 2026 15:47:49 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Francesco Valla <francesco@...la.it>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Jonathan Corbet <corbet@....net>, Jocelyn Falempe <jfalempe@...hat.com>, 
	Javier Martinez Canillas <javierm@...hat.com>, Sam Ravnborg <sam@...nborg.org>, 
	Mario Limonciello <mario.limonciello@....com>, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org, 
	linux-embedded@...r.kernel.org
Subject: Re: [PATCH RFC v2 1/3] drm: client: add splash client

Hi Franceso,

On Tue, 6 Jan 2026 at 15:26, Francesco Valla <francesco@...la.it> wrote:
> Add a DRM client that draws a simple splash, with possibility to show:
>
>   - a colored background;
>   - a static BMP image (loaded as firmware);
>   - the logo provided by EFI BGRT.
>
> The client is not meant to replace a full-featured bootsplash, but
> rather to remove some complexity (and hopefully boot time) on small
> embedded platforms or on systems with a limited scope (e.g: recovery
> or manufacturing images).
>
> The background color can be set either at build time from a dedicated
> config option or at runtime through the drm_client_lib.splash_color
> command line parameter. Any color in RGB888 format can be used.
>
> If enabled, the static BMP image is loaded using the kernel firmware
> infrastructure; a valid BMP image with 24bpp color and no compression
> is expected. The name of the image can be set through the
> drm_client_lib.splash_bmp kernel command line parameter, with the
> default being 'drm_splash.bmp'.
>
> Just like the existing DRM clients, the splash can be enabled from the
> kernel command line using drm_client_lib.active=splash.
>
> Signed-off-by: Francesco Valla <francesco@...la.it>

Thanks for your patch!

> --- /dev/null
> +++ b/drivers/gpu/drm/clients/drm_splash.c

> +#if IS_ENABLED(CONFIG_DRM_CLIENT_SPLASH_BMP_SUPPORT)

There is no need to protect this block with #if, as it does not generate
any code.

> +#define BMP_FILE_MAGIC_ID 0x4d42
> +
> +/* BMP header structures copied from drivers/video/fbdev/efifb.c */
> +struct bmp_file_header {
> +       u16 id;
> +       u32 file_size;
> +       u32 reserved;
> +       u32 bitmap_offset;
> +} __packed;
> +
> +struct bmp_dib_header {
> +       u32 dib_header_size;
> +       s32 width;
> +       s32 height;
> +       u16 planes;
> +       u16 bpp;
> +       u32 compression;
> +       u32 bitmap_size;
> +       u32 horz_resolution;
> +       u32 vert_resolution;
> +       u32 colors_used;
> +       u32 colors_important;
> +} __packed;
> +#endif // CONFIG_DRM_CLIENT_SPLASH_BMP_SUPPORT

As per [1], all these values are little-endian.  Hence they should
be declared as such using le16 or le32, and accessed using
get_unalined_le{16,32}().

[1] https://en.wikipedia.org/wiki/BMP_file_format#File_structure

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds