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xfree86: fbdevhw: fix pci detection on recent Linux 

Linux kernel v6.9 has changed the symlink to point to the parent device. This
breaks fbdev_open() detection logic. Change it to use the subsystem symlink
instead which will remain stable.

Kernel v6.8:

[    14.067] (II) fbdev_open() sysfs_path=/sys/class/graphics/fb0
[    14.067] (II) fbdev_open() buf=../../devices/platform/vesa-framebuffer.0/graphics/fb0

Kernel v6.9:

[    15.609] (II) fbdev_open() sysfs_path=/sys/class/graphics/fb0
[    15.609] (II) fbdev_open() buf=../../devices/pci0000:00/0000:00:01.0/vesa-framebuffer.0/graphics/fb0

Originally found in automated Debian ISO QA testing [0] and confirmed in Linux [1].

Tested on kernels v6.9.7 and v6.8.12

[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1075713
[1] https://lore.kernel.org/lkml/lLyvPFC_APGHNfyGNHRpQy5izBikkaTPOpHooZIT3fFAoJPquSI31ZMueA99XTdr8ysir3X7O7IMdc6za-0m79vr_claeparHhoRouVgHOI=@proton.me/

Fixes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1714
Signed-off-by: Tj <tj.iam.tj@proton.me>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1612>
This commit is contained in:
Tj 2024-07-19 19:50:56 +02:00 committed by Marge Bot
parent a136ce3d57
commit 728b54528d
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
hw/xfree86/fbdevhw/fbdevhw.c
View File

@ -378,9 +378,9 @@ fbdev_open(int scrnIndex, const char *dev, char **namep)
node++;
}
if (asprintf(&sysfs_path, "/sys/class/graphics/%s", node) < 0 ||
if (asprintf(&sysfs_path, "/sys/class/graphics/%s/device/subsystem", node) < 0 ||
readlink(sysfs_path, buf, sizeof(buf) - 1) < 0 ||
strstr(buf, "devices/pci")) {
strstr(buf, "bus/pci")) {
free(sysfs_path);
close(fd);
return -1;