Synaptics LED support

[George Sedov]

Hi all,

Some synaptics touchpads have a LED embedded to the upper-left corner,
which is supposed to be used to disable the touchpad by double-tapping
it. In linux, the proper support for it was never mainlined.

There were a couple of out-of-tree patches (can be found here
https://github.com/perusio/xorg-synaptics-led-support) which supposedly
came from SUSE enterprise, but they were never really finished. One of
the two patches is for the kernel, to support the LED itself, and the
other one for the Xorg driver, to support the double tap.

The Xorg driver relied on the kernel to distinguish the supported
devices (double tap worked if the sys-file for the LED was present), and
the kernel should have relied on the device properties to distinguish
them, but that part was the one that  was never finished. The particular
device ID was inserted instead, which made the driver useless for all
but one touchpad models.

Is there any chance this LED functionality can be supported in libinput?
What can be done about it? Maybe I can be of some help. I would really
love to see this functionality in linux, even if 4 years later.

Cheers,
	George