Bug 84101

Summary:	Brightness interface shown in desktop computer with Intel graphics i915
Product:	ACPI	Reporter:	Alicia Boya García (ntrrgc)
Component:	Power-Video	Assignee:	Aaron Lu (aaron.lu)
Status:	CLOSED WILL_NOT_FIX
Severity:	normal	CC:	bugzilla, rui.zhang
Priority:	P1
Hardware:	Intel
OS:	Linux
Kernel Version:	3.16.1	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	`acpidump` output

Description Alicia Boya García 2014-09-08 17:31:59 UTC

For some reason the kernel detects an `acpi_video0` in /sys/class/backlight even though it is running in a desktop computer whose monitors don't support editing backlight levels on software.

`/sys/class/backlight/acpi_video0/device` is a symlink to the integrated graphic card, listed on `lspci` as the following:

00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller (rev 09)

Comment 1 Alicia Boya García 2014-09-08 17:43:18 UTC

This is causing GNOME to display brightness controls on my computer which does not support them.

https://bugzilla.gnome.org/show_bug.cgi?id=736270#c4

Comment 2 Zhang Rui 2014-09-15 07:56:36 UTC

please attach the acpidump output.

Comment 3 Alicia Boya García 2014-09-15 07:59:39 UTC

Created attachment 150421 [details]
`acpidump` output

Comment 4 Aaron Lu 2014-09-15 08:47:56 UTC

I can think of two ways to solve this problem:
1 Add your system into a DMI table to disable the acpi video interface;
2 Disable acpi video interface for all systems that are desktops, which can be queried from the "PM Profile" field of the FADT table.

I think we can try option 2.

Comment 5 Alicia Boya García 2014-09-15 08:50:00 UTC

Please notice some desktops have brightness interfaces indeed, e.g. HP All in One or iMac computers.

Comment 6 Aaron Lu 2014-09-15 08:53:40 UTC

And that acpi_video interface actually works? If that is the case, we can only do quirk then...

Comment 7 Alicia Boya García 2014-09-15 08:56:47 UTC

For my desktop computer without brightness interface, obviously not. About the all in one computers mentioned above, I don't know.

I faintly recall using once Linux in an iMac, but I don't recall whether brightness controls worked or not.

Anyway, I don't think breaking the brightness interface for such computers is a good idea.

Comment 8 Aaron Lu 2014-10-24 08:18:44 UTC

I don't see a way to solve this problem exposed by firmware, I'll close the bug as will_not_fix.