Re: Bug#1141604: linux-image-6.12.94+deb13-amd64: does not detect ScreenPad on ASUS VivoBook

[Salvatore Bonaccorso <carnil@debian.org>]

Hi all,

On Fri, Jul 10, 2026 at 03:31:08PM +0300, Ilpo Järvinen wrote:
> On Fri, 10 Jul 2026, Denis Benato wrote:
> > On 7/9/26 22:08, Salvatore Bonaccorso wrote:
> > > Control: forwarded -1 https://lore.kernel.org/regressions/178362762638.911488.8564892548331679884@eldamar.lan
> > > Control: tags -1 + upstream
> > >
> > > Hi,
> > >
> > > Ponali reported in Debian (https://bugs.debian.org/1141604) the
> > > following issue after updating from 6.12.90 to 6.12.94. First quoting
> > > the report:
> > >
> > > On Tue, Jul 07, 2026 at 07:37:24AM +0200, Ponali wrote:
> > >> Package: src:linux
> > >> Version: 6.12.94-1
> > >> Severity: normal
> > >> Tags: upstream, regression
> > >> X-Debbugs-Cc: ponali2k@gmail.com
> > >>
> > >> Last known working kernel: 6.12.90-1
> > >> First known broken kernel: 6.12.94-1
> > >>
> > >>
> > >> Dear Maintainer,
> > >>
> > >> I upgraded all my packages through apt, which also upgraded the linux image
> > >> from 6.12.90 to 6.12.94.
> > >>
> > >> I expected the ScreenPad display to continue to be detected and exposed as a
> > >> DRM output, like on 6.12.90. The ScreenPad being the trackpad with a screen,
> > >> which came with my computer (ASUS VivoBook X532FA_S532FA).
> > >>
> > >> After upgrading and rebooting, the new kernel caused a regression where the
> > >> display of the ScreenPad fails to get recognized by the kernel. The touchpad
> > >> functionality still works. Usually, the ScreenPad would appear as "HDMI-A-1".
> > >> The DRM connector for it still exists (/sys/class/drm/card0-HDMI-A-1), but
> > >> "status" reports "disabled"
> > >>
> > >> I could not get the ScreenPad display to be recognized again on the new kernel,
> > >> so I configured GRUB to automatically boot to the 6.12.90 kernel through the
> > >> "Advanced Options". The ScreenPad is recognized on older kernel versions, so I
> > >> am still able to use it (until a new LPE comes around).
> > >>
> > >> To replicate:
> > >> 1. Boot with 6.12.90. The ScreenPad display is detected as HDMI-A-1.
> > >> 2. Boot with 6.12.94 with the exact same hardware.
> > >> 3. The ScreenPad display is no longer usable.
> > >>
> > >>
> > >> My main display is eDP-1 (1920x1080), though it isn't essential. My GPU is an
> > >> integrated Intel iGPU, and the driver used for both screens is i915. I have
> > >> booted to the new kernel for reportbug to get all the information
> > >> automatically, but i will continue to use the old one until the appropriate
> > >> time.
> > > Now, Ponali did bisect the changes between 6.12.90 and 6.12.94 and
> > > found that the backport of the commit 8d95d1f4aa5c ("platform/x86:
> > > asus-wmi: fix screenpad brightness range") changed the behaviour.
> > > Bisect log is at: https://bugs.debian.org/1141604#22
> > >
> > > As this change was backported to other stable series as well I asked
> > > Ponali to please test 7.0.y and 7.1.y and confirmed that both 7.0.13
> > > and as well 7.1.3 show the hehaviour.
> > >
> > > #regzbot introduced: 8d95d1f4aa5c76202b0833a70998769384612488
> > > #regzbot link: https://bugs.debian.org/1141604
> > >
> > > Is there anything Ponali can report back to further debug the issue?
> > Hi Salvatore,
> > 
> > The commit incriminated is this one: https://lore.kernel.org/all/20260302174431.349816-3-denis.benato@linux.dev/
> > 
> > As you can see that commit changes min/max of the brightness range, but 
> > does not touch the detection at all, 
> 
> To be more precise, it DOES change read_screenpad_backlight_power() -> 
> asus_wmi_get_devstate_simple() but AFAICT that cannot make things worse 
> because asus_wmi_get_devstate_simple() used in both cases, so I was 
> left to wonder the same thing as you.
> 
> That being said, it's hard to see how bisect could point this to a wrong 
> commit either because good/bad should be pretty obvious.
> 
> Did reverting the suspect commit on top of 6.12.94 result in a working 
> system?

Ponali did test, and reported back in the Debian bug at
https://bugs.debian.org/1141604#60, quoting:

> I have found the sysfs attribute for brightness control to be in
> /sys/class/backlight/asus_screenpad, and it appears on both 6.12.90 and
> 6.12.94.
> 
> On 6.12.90, max_brightness reports 235.
> 
> On 6.12.94, max_brightness reports 255.
> 
> 
> I have checked out to v6.12.94, reverted the suspect commit, and found
> the ScreenPad to be working as intended.
> 
> 
> Regards,
> 
> Ponali

Regards,
Salvatore