Re: [PATCH 0/9 v2] Synaptics image sensor support

On 07/20/2011 06:38 AM, djkurtz@chromium.org wrote:

From: Daniel Kurtz <redacted>
Patches 4-7 add up to 3 finger support for image sensor touchpads.
Image sensors do not suffer from the finger tracking issues that plagued
the earlier "profile sensors", and which required the invention of "semi-mt"
(Semi-mt reports a bounding box around two fingers instead of the fingers
themselves).  Instead, the image sensors report the actual positions of two
fingers using the same "Advanced Gesture Mode".  This driver uses two MT-B slots
to report these two fingers to userspace.  In addition, it will also report
the total number of fingers using BTN_TOOL_*TAP EV_KEY events.
Userspace drivers should be aware that the number of fingers reported via
BTN_TOOL_*TAP can be greater than the total number MT-B slots with non-negative
track_ids.  Upon opening the device node, userspace should query the maximum
values supported ABS_MT_SLOT, and note the number of supported BTN_TOOL_*TAP
events.

I would still rather see a new property bit for devices that track and
report different numbers of touches. I think it is worthwhile to be
explicit here rather than leave it up to voodoo magic in userpace drivers.

This and the touch count transition issue I brought up in a reply to
patch 7 are my only concerns with this part of the patchset.

BTW, I found the commit messages and the code to be very comprehensible.
Good job on cleaning them up!

-- Chase