[Intel-gfx] [PATCH v3 4/4] thinkpad-acpi: fix handle locate for video and query of _BCL

[Henrique de Moraes Holschuh]

On Thu, 26 Sep 2013, Aaron Lu wrote:
> I checked the git log for the commit to use tpacpi_acpi_handle_locate to
> locate video controller's ACPI handle, it's:
> 
> commit 122f26726b5e16174bf8a707df14be1d93c49d62
> Author: Henrique de Moraes Holschuh <hmh at hmh.eng.br>
> Date:   Mon Aug 9 23:48:18 2010 -0300

Yeah...

> So I checked out that commit and found that it shouldn't work either,
> since it has the same problem of the current code.
> 
> The ACPI video controller device is given an id of ACPI_VIDEO_HID, but
> it's only known to Linux ACPI, not ACPICA, so the function provided by
> ACPICA acpi_get_devices will not work in this case, as that function will
> really check the control method of _HID under the handle, which does not
> exist no matter if Linux ACPI has added an id to its device structure or
> not. OTOH, the function provided by Linux ACPI acpi_device_hid will see
> the added id. In a word, the add of the HID will not affect the ASL
> namespace layout of the device node(thus, no _HID control method will
> be added to the device node).

Erk.  It went broken for a long time, and the users didn't notice(!)...

> commit ff413195e830541afeae469fc866ecd0319abd7e
> Author: Alex Hung <alex.hung at canonical.com>
> Date:   Tue Apr 24 16:40:52 2012 +0800
> 
>     thinkpad-acpi: fix issuing duplicated key events for brightness up/down
>     
>     The tp_features.bright_acpimode will not be set correctly for brightness
>     control because ACPI_VIDEO_HID will not be located in ACPI. As a result,
>     a duplicated key event will always be sent. acpi_video_backlight_support()
>     is sufficient to detect standard ACPI brightness control.
>     
>     Signed-off-by: Alex Hung <alex.hung at canonical.com>
>     Signed-off-by: Matthew Garrett <mjg at redhat.com>

Until that.  And unfortunately I did not connect the dots at the time.

Thanks for explaining the issue properly.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh