Control: tags -1 + moreinfo upstream
On Sat, Jun 20, 2026 at 12:37:05PM +0200, Andreas Weber wrote:
> Package: linux-image-amd64
> Version: 6.12.90-2
> Severity: normal
>
> After upgrading from 6.12.88-1 to 6.12.90-2, display mirroring (clone mode)
> no longer works on GNOME/Wayland. The external display is detected and
> works in extended mode, but mirroring cannot be activated via GNOME
> Settings → Displays.
> Reverting to 6.12.88-1 resolves the issue.
Can you please bisect the changes between 6.12.88 and 6.12.90 upstream
to identify the breaking commit? That would involve compiling and
testing a few kernels:
git clone --single-branch -b linux-6.12.y
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
cd linux-stable
git checkout v6.12.88
cp /boot/config-$(uname -r) .config
yes '' | make localmodconfig
make savedefconfig
mv defconfig arch/x86/configs/my_defconfig
# test 6.12.88 to ensure this is "good"
make my_defconfig
make -j $(nproc) bindeb-pkg
... install the resulting .deb package and confirm problem does not exist
# test 6.12.90 to ensure this is "bad"
git checkout v6.12.90
make my_defconfig
make -j $(nproc) bindeb-pkg
... install the resulting .deb package and confirm problem exists
With that confirmed, the bisection can start:
git bisect start
git bisect good v6.12.88
git bisect bad v6.12.90
In each bisection step git checks out a state between the oldest
known-bad and the newest known-good commit. In each step test using:
make my_defconfig
make -j $(nproc) bindeb-pkg
... install, try to boot / verify if problem exists
and if the problem is hit run:
git bisect bad
and if the problem doesn't trigger run:
git bisect good
. Please pay attention to always select the just built kernel for
booting, it won't always be the default kernel picked up by grub.
Iterate until git announces to have identified the first bad commit.
Then provide the output of
git bisect log
In the course of the bisection you might have to uninstall previous
kernels again to not exhaust the disk space in /boot. Also in the end
uninstall all self-built kernels again.
Regards,
Salvatore
