Re: [PATCH V3 1/3] Input: cyttsp - Cypress TTSP capacitive multi-touch screen support

On Tue, Sep 27, 2011 at 1:52 PM, Henrik Rydberg [off-list ref] wrote:

Hi Javier,

quoted

Cypress TrueTouch(tm) Standard Product controllers are found in
a wide range of embedded devices. This driver add support for a
variety of TTSP controllers.

please find some comments below.

Hello Henrik,

I solved most of the issues you point me out, I have just a small
question about one of them:

quoted

+     }
+
+     for (i = 0; i < CY_MAX_ID; i++) {
+             if (ts->slot_prev[i] == CY_USED &&
+                 ts->slot_curr[i] == CY_UNUSED)
+                     cyttsp_report_slot_empty(ts->input, i);
+             ts->slot_prev[i] = ts->slot_curr[i];
+             ts->slot_curr[i] = CY_UNUSED;
+     }

Input core handles duplicate calls, so the above could be simplified.

That means that the input MT is able to handle duplicates and I can
send the state of all the contacts and it will be able to identify the
deltas to send to user-space? Or do I have to keep the deltas and only
call input_mt_report_slot_state() when I detect that a finger that was
previously down was lifted?

To be more precise, the correct approach is:

	for (i = 0; i < CY_MAX_ID; i++)
		if (!(used & (1 << i)))
			cyttsp_report_slot_empty(ts->input, i);

or

	for (i = 0; i < CY_MAX_ID; i++)
		if (previous & (1 << i) &&
		    !(used & (1 << i)))
			cyttsp_report_slot_empty(ts->input, i);

where used is a bitmask to store each contact state for this event and
previous is a bitmask to store the state for the previous event.

I looked at input_mt_report_slot_state() and it seems that it only
checks whether the active parameter to send an ABS_MT_TRACKING_ID -1
input event, so I think that I should use the latter.

Thank you and best regards,

-- 
Javier Martínez Canillas
(+34) 682 39 81 69
Barcelona, Spain
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