Bug#651741: gnome-power-manager: display backlight brightness has no effect on Sony Vaio VPCYA1V9E

[Kalle Olavi Niemitalo]

package gnome-power-manager
reassign 651741 xserver-xorg-video-intel
quit

Kalle Olavi Niemitalo <kon at iki.fi> writes:

> So, the next thing I'll try will be moving it back to the top.

That works, and I no longer think gnome-power-manager should
be changed, so I'm reassigning the bug.

Please change intel_output_backlight_init() in
xserver-xorg-video-intel to prefer the "intel_backlight"
device rather than "acpi_video0", at least on
Sony Vaio VPCYA1V9E.  This should be done because
/sys/class/backlight/acpi_video0/brightness does not
affect the brightness of the backlight on this machine but
/sys/class/backlight/intel_backlight/brightness does.

On other machines, I think it would be safest to keep using
acpi_video0, so as not to cause new bugs.  I'm not sure what
would be the best way for xserver-xorg-video-intel to detect this
laptop model.  I can think of these ways:

(a) User override via xorg.conf, documented in intel(4).
    Would be OK for knowledgeable users, but difficult to
    find for others, especially if it is initially not even
    clear that the backlight is controlled via the X server.

(b) PCI subsystem.  Here, lspci -vn shows:

    00:02.0 0300: 8086:0046 (rev 02) (prog-if 00 [VGA controller])
            Subsystem: 104d:907c

    intel_driver.h defines the SUBVENDOR_ID and SUBSYS_ID macros,
    which intel_output_backlight_init could use on
    intel_get_screen_private(output->scrn)->PciInfo.
    The problem with this is that the subsystem ID might cover
    more laptop models than necessary.

(c) Manufacturer and product name from DMI.
    I don't know how to read these in xserver-xorg-video-intel.

(d) Version or checksum of ACPI DSDT, so that the workaround will
    be automatically disabled if the firmware is upgraded.
    Here, iasl -d shows:

    * Original Table Header:
    *     Signature        "DSDT"
    *     Length           0x0000ACA8 (44200)
    *     Revision         0x02
    *     Checksum         0x39
    *     OEM ID           "Sony"
    *     OEM Table ID     "VAIO"
    *     OEM Revision     0x20101102 (537923842)
    *     Compiler ID      "MSFT"
    *     Compiler Version 0x01000013 (16777235)

At this time, I like approach (b) best.

Ender Akduman <enderakduman at gmail.com> writes:

> By the way do you mean 'backlight' instead of 'backlist' in:
> (...when it was renamed from "intel" to "intel_backlist")

Thank you for the correction.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: not available
URL: <http://lists.alioth.debian.org/pipermail/pkg-gnome-maintainers/attachments/20120115/f3832292/attachment.pgp>