Differential D55175
linuxkpi: Add device under parent, not under class Authored by dumbbell on Feb 8 2026, 10:55 AM. Tags None Referenced Files
Details
In device_add(), the function used to add the given device under its class. This is used to build a sysctl tree. We ended up with devices or "pseudo" devices (like the output connectors of a GPU). For example with an output connector: sysctl sys.class.drm.card0-DP-1 This device should be added under its parent if it has one. With this fix, the same output connector is now: sysctl sys.device.drmn1.card0.card0-DP-1 Sponsored by: The FreeBSD Foundation
Diff Detail
Event TimelineComment Actions I dislike this idea. Comment Actions Here is an example on a computer running Linux 6.18: # ls -l /sys/class/drm total 0 lrwxrwxrwx 1 root root 0 9 mars 2026 card0 -> ../../devices/pci0000:00/0000:00:08.1/0000:17:00.0/drm/card0 lrwxrwxrwx 1 root root 0 9 mars 2026 card0-DP-3 -> ../../devices/pci0000:00/0000:00:08.1/0000:17:00.0/drm/card0/card0-DP-3 lrwxrwxrwx 1 root root 0 9 mars 2026 card0-DP-4 -> ../../devices/pci0000:00/0000:00:08.1/0000:17:00.0/drm/card0/card0-DP-4 lrwxrwxrwx 1 root root 0 9 mars 2026 card0-DP-5 -> ../../devices/pci0000:00/0000:00:08.1/0000:17:00.0/drm/card0/card0-DP-5 lrwxrwxrwx 1 root root 0 9 mars 2026 card0-HDMI-A-3 -> ../../devices/pci0000:00/0000:00:08.1/0000:17:00.0/drm/card0/card0-HDMI-A-3 ... So the correct path on Linux is /sys/devices/pci0000:00/0000:00:08.1/0000:17:00.0/drm/card0/card0-DP-3. The difference with my proposal is that they use the PCI address (pci0000:00/0000:00:08.1/0000:17:00.0/drm), and here, we have the device name (drmn0). The other difference is that they use plural for "devices" while we use the singular "device". The file in /sys/class/drm/... is a symlink to /sys/devices/.... I don’t find the use of /sys/class/drm logical, as the connector should be a child of the device, not a class. Let’s collect other opinions :-) |