Re: [PATCH v3 7/7] Input: elantech - add v3 hardware support

On Fri, 26 Aug 2011 09:28:13 -0500, Seth Forshee [off-list ref] wrote:

On Fri, Aug 26, 2011 at 09:03:11AM +0800, JJ Ding wrote:

quoted

+	/*
+	 * check debounce first, it has the same signature in byte 0 

Just one pedantic comment -- git complained about trailing whitespace on
this line. Not that important, and Dmitry can clean it up when he
applies the patch if he's so inclined.

This patch looks good now, and it's testing fine for me.

Reviewed-and-Tested-by: Seth Forshee [off-list ref]

Thank you very much for viewing and testing this code, Seth.

I'm also curious what you found out about whether or not the touchpad
does accurate finger tracking. I've played with it a little, and the
finger tracking has been accurate except for one small exception. When
the fingers are overlapping on one axis the touchpad always reports the
same position for both fingers along that axis. For instance, if I move
one finger up and the other finger down simultaneously on the touchpad,
one of the fingers will show reverse movement on the y axis briefly
while the fingers overlap. But I've never seen the fingers swap between
the two frames of the packet.

I just got confirmed that with v3, two finger touch always gets reported
separately. I will resend this series for this update.
Add what you observed is actually hardware limitation. The v3 hardware
only has a projective sensor. When two fingers are overlapping along x or
y axis, the hardware can only sense one on that axis, once the two
fingers are away from the "crossing zone", they get reported separately again.

jj

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