[SRU][R/S][PATCH 0/1] Fix incorrect boot_display reporting on multi-GPU systems

[Aaron Ma]

BugLink: https://bugs.launchpad.net/bugs/2161036

SRU Justification:

[Impact]
On multi-GPU systems, a VGA-compatible device that is not driving the display
can incorrectly be reported as the primary graphics device through the
boot_display sysfs attribute.

[Fix]
Apply upstream commit 596b3678326d3d1aed7c19423b6746f1ce09688a
("x86/video: Only fall back to vga_default_device() without screen info").

When framebuffer screen information is valid, use it exclusively to identify
the primary device. Fall back to vga_default_device() only when no framebuffer
has been set up.

[Test Plan]
Boot a multi-GPU system and verify that boot_display identifies only the GPU
backing the framebuffer. Verify fallback behavior when no framebuffer has
been initialized.

[Where problems could occur]
The change is limited to primary display-device detection in
arch/x86/video/video-common.c. The main risk is incorrect identification of the
primary GPU on systems with unusual or incomplete framebuffer information.

Mario Limonciello (1):
  x86/video: Only fall back to vga_default_device() without screen info

 arch/x86/video/video-common.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

-- 
2.43.0