[ltp] tpacpi bug in tpacpi::thinklight/brightness for X1 Carbon

Henrique de Moraes Holschuh linux-thinkpad@linux-thinkpad.org
Mon, 30 Dec 2013 00:15:42 -0200

On Sun, 29 Dec 2013, Sandro wrote:
> The Lenovo X1 Carbon is gaining populairty as it's easily one of the
> prettiest alternatives to the McBook Air.
> For a while, I thought the keyboard backlight couldn't be controlled
> through tpacpi, period. After asking a question <
> http://askubuntu.com/questions/383501/> I got an interesting answer:
> The keyboard backlight can in fact be turned off using the following
> command:
> echo 0 > /sys/class/leds/tpacpi\:\:thinklight/brightness
> It's just that it cannot be turned /on/, which is what I am trying to do.
> I can't be certain, but if the current tpacpi can turn the light off, it
> gives me the impression that turning it on is just a bugfix away.
> I cannot find an issuetracker for Github or Sourceforce, so I thought maybe
> one of the devs (is that still Henrique de Moraes Holschuh AKA Hmh?) will
> read this.

I am reading this, but I can't do much without access to a X1.  The
thinklight control uses a specific ACPI method, so your X1 has it or it
would not have turned anything off.

It likely wants a different parameter to enable the keyboard backlight
(which stands to reason, since it is not a thinklight).  Since the turn-off
command worked, if we're lucky it is a bitfield and it can be used to
separately control the thinklight and the keyboard backlight.

I won't promise anything, but send me the ACPI dump of your X1 (update it to
the latest BIOS/EFI first).  Use a recent version of the ACPI tools,
preferably "acpidump" from the latest Linux kernel tree (it is inside the
tools/power/acpi directory of the kernel source.  Type Make there to build).
Your linux distro might have it packaged.

I also need the output of dmidecode.  Remove all serial numbers and UUIDs
before you send it to me (replace their digits with "X").

  "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