Thomas Zimmermann 1eb4d744fb drm/cirrus-qemu: Stricter mode validation
Implement strict checking of a display mode's minimum scanline
pitch in cirrus_mode_config_mode_valid(). Sort out all modes that
possibly overflow the maximum pitch.

The current validation only tests against a display mode's minimum
requirements for video memory. Only atomic_check later tests against
the pitch limit before programming the framebuffer.

The problem is that user-space compositors do not handle this
gracefully. If atomic_check fails to validate the scanline pitch
and returns an error, the compositor, namely Weston, does nothing
and the display remains stale.

Ruling out display modes that possibly overflow the pitch avoids
this problem. With only 4 MiB of video memory available, this
effectively limits horizontal resolution to 800 pixels. But with
cirrus-qemu being low-end and obsolete, this is probably not an
issue in practice. Better alternatives are available in qemu.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://lore.kernel.org/r/20250328091821.195061-3-tzimmermann@suse.de
2025-04-01 15:35:12 +02:00
2025-02-25 17:36:09 +10:00
2024-09-01 20:43:24 -07:00
2025-02-25 17:36:09 +10:00
2025-02-04 11:27:45 -05:00
2025-02-25 11:43:10 +01:00
2022-09-28 09:02:20 +02:00
2025-02-23 12:32:57 -08:00
2024-03-18 03:36:32 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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