Screen-privacy couldn't work

Cause the 5.15.0-23-generic couldn't support it, I used 5.17 mainline kernel.

$ cat /proc/acpi/ibm/lcdshadow
status: 0
commands: 0, 1

And after press the Fn + D, the screen display angle changed, and the content of /proc/acpi/ibm/lcdshadow is changed, and the GUI of 'Restrict Viewing Angle' is synced between on and off. But we could control from 'Restrict Viewing Angle' in g-c-c.

Here is the bug for kernel.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1966061

The kernel support landed in 5.17 only yes.

Marco, do we have a way to hide the UI if the kernel support is missing?

@seb,

 It's buggy even on 5.17 kernel, we could not control from g-c-c. Thanks!

So, I've checked with the latest kernel, but the KMS properties aren't either showing:

proptest | grep privacy -A3
 98 privacy-screen sw-state:
  flags: enum
  enums: Disabled=0 Enabled=1
  value: 0
 99 privacy-screen hw-state:
  flags: immutable enum
  enums: Disabled=0 Enabled=1 Disabled-locked=2 Enabled-locked=3
  value: 0

However, with properly compiled kernel I noticed there are also issues, I think that's due to some recent upstream changes to the initial patch, I'll check that again.

> Marco, do we have a way to hide the UI if the kernel support is missing?

Ah, I missed the question... Indeed if the feature is not supported, there's no UI visible.

Ok, got it...

It was due to the triple-buffering patch that was ignoring the pending update, see
  https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1441#note_1428961

This bug was fixed in the package mutter - 42.0-3ubuntu1

---------------
mutter (42.0-3ubuntu1) jammy; urgency=medium

  [ Marco Trevisan (Treviño) ]
  * debian/patches: Cherry-pick various upstream commits for 42.1:
    + onscreen/native: Fall back if COPY_MODE_SECONDARY_GPU fails to init
      (LP: #1964037, #1959888)
  * debian/patches: Allow any drag timestamp as drag start serial (LP: #1964541)
  * debian/patches: Move x11-fractional scaling under ubuntu namespace
  * debian/patches: Account ClutterStage grabs on Wayland key focus sync
    (LP: #1964442)
  * debian/libmutter-10-0.symbols: Update including new internal symbols
  * debian/patches: Avoid memory errors when comparing gamma values
  * debian/patches: Fix privacy-screen and connectors updates with
    triple-buffering (LP: #1966178)
  * debian/patches: Ensure privacy screen settings are applied on startup
    (LP: #1966178)

  [ Jeremy Bicha ]
  * Merge from Debian unstable. Remaining changes:
    - debian/patches/x11-Add-support-for-fractional-scaling-using-Randr.patch:
      + X11: Add support for fractional scaling using Randr
    - Add triple-buffering patch
    - debian/libmutter-10-0.symbols: Add symbols for triple buffering patch
    - ubuntu/wayland-data-device-Allow-any-drag-timestamp-as-drag-star.patch:
      + handle DnD for old (snapped) gtk apps that used wrong wayland serials

mutter (42.0-3) unstable; urgency=medium

  [ Marco Trevisan (Treviño) ]
  * debian/patches: Cherry-pick upstream fixes targeting 42.1
  * debian/patches: Ensure repick happens on actors visibility changed
    (LP: #1964545)

  [ Jeremy Bicha ]
  * Release to unstable

 -- Marco Trevisan (Treviño) <email address hidden> Wed, 13 Apr 2022 03:30:39 +0200

I proposed a fix upstream in:
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1441#note_1429238
but can't test it myself.

Comment #7 leads me to find it was instead declared fixed in:
monitor-manager-Ensure-monitors-settings-after-backend-ha.patch

Should I revert my experimental fix from !1441?

Nope, I handled it as I mentioned in the previous upload as I needed something done by FF, but we can reiterate this easily with a fix on next mutter upload.

It shouldn't lead to any problem, isn't it?

Tested on 5.17.0-1003-oem kernel, this privacy item could be showed.

But it couldn't sync with 'Fn + D', if it is disabled, click the 'Fn + D', it changed enabled, and changed back to disabled quickly. Looks like it's a kind of bug.

Tested my own build image based on 5.15.0-27-generic with upstream patches, it works perfectly. So the new issue might be related kernel side.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1966061/comments/3

Tested kernel are here.
https://people.canonical.com/~binli/5.15.0-27.28binli1/