acpi_video: dim the internal panel while the lid is closed

[seuros]

Summary

Register an acpi_lid_event consumer that saves the current _BQC level and
drives _BCM to the lowest level _BCL offers when the lid closes, putting
the saved level back when it opens. Only an output already classified as
an internal panel is touched, and only a level this handler dimmed is
restored, so a brightness change made while the lid was shut survives.

Disabled by default; set hw.acpi.video.lid_blank=1 to enable.

[ngie]

Disabled by default; set hw.acpi.video.lid_blank=1 to enable.

Why disabled instead of enabled by default? Seems like it would be a good idea to not have a laptop with a shut lid overheat the system :).

sys/dev/acpica/acpi_video.c

550–553

Why 3? Could this be made into a constant instead?

554–555

[ngie]

sys/dev/acpica/acpi_video.c

550–553

Why 3? Could this be made into a constant instead?

Alternatively, could you use nitems(..) to dynamically calculate the size instead of using 3..?

579–583

[dteske]

I second what @ngie said -- seems like default should be enabled (POLA and all)

[seuros]

The disabled by default was because i want to land it, ask current@ and other testers to enable it.
If there are no report of boards that misfire randomly , then followup with a default enabled before 16 release.

I personally will be pretty pissed if i update the kernel, have acpi_video enabled and start having my screen glitching,
unlike acpi_apple, this driver already exists.

Apple dont have this knob because i tested in every laptop model that existed.

[seuros]

Switched to a named constant, BCL_FIRST_LEVEL, alongside the existing
BCL_FULLPOWER/BCL_ECONOMY just above it. 3 is not an array size:
it returns the full-power level at [0], the economy level at [1], and the
selectable levels from [2]

[ngie]

This is reasonable to me 👍. Waiting for feedback from the ACPI folks before providing a ship-it.