On Wed, Aug 17, 2011 at 10:05:48PM +0800, Daniel Kurtz wrote:

On Mon, Aug 15, 2011 at 3:17 PM, Daniel Kurtz [off-list ref] wrote:

quoted

Hi Henrik,

Thanks for the great feedback.

On Sat, Aug 13, 2011 at 5:09 AM, Henrik Rydberg [off-list ref] wrote:

quoted

Hi Daniel,

looks good, some details below.

The ABS_MT_TOUCH_MAJOR is supposed to have zero intercept, to remain
compatible with user space handling of type A devices. Also, the scale
should match the screen/pad size, such that the actual size of the
touch area can be deduced. In addition, based on the current sensor
technologies, ABS_MT_PRESSURE and ABS_MT_TOUCH_MAJOR are normally
mutually exclusive.

All in all, I would prefer to only report width via (the single-finger
axis) ABS_TOOL_WIDTH, and only for compatibility reasons.

+
+static void synaptics_report_slot_agm(struct input_dev *dev, int slot,
+                                   const struct synaptics_hw_state *agm)
+{
+     input_mt_slot(dev, slot);
+     input_mt_report_slot_state(dev, MT_TOOL_FINGER, true);
+     input_report_abs(dev, ABS_MT_POSITION_X, agm->x);
+     input_report_abs(dev, ABS_MT_POSITION_Y, invert_y(agm->y));
+     input_report_abs(dev, ABS_MT_PRESSURE, agm->z);
+}

With ABS_MT_TOUCH_MAJOR dropped, sgm and agm seems to coincide...
....

quoted

Looks good otherwise.

Thanks,
Henrik

Ahh....  ok, this makes sense.  I missed this detail previously.
Basically:
 * Only report synaptics "w" as ABS_TOOL_WIDTH (for backwards compatibility)
 * Report synaptics "z" as ABS_MT_TOUCH_MAJOR (assuming it is really
'width of finger in surface units'), and ABS_PRESSURE (for backwards
compatibility).
 * Don't use ABS_MT_PRESSURE.
 * This will simplify agm/sgm reporting by making them both reoprt
the same axes.

Hi Henrik,

I think I was wrong in my previous comment.

I agree we should drop reporting synaptics 'w' (4-15, arbitrary units)
in ABS_MT_TOUCH_MAJOR.
Instead, to support legacy, report 'w' in ABS_TOOL_WIDTH, and do not
report ABS_MT_TOUCH_MAJOR at all.

However, I believe we should still report synaptics 'z' (0-255, in
arbitrary units) as ABS_MT_PRESSURE.
This will, in turn, be used by input_mt_report_pointer_emulation() to
determine the correct ABS_PRESSURE to report for legacy userspace
uses.

Alternatively, you can use input_mt_set_value() to save Z value to be
used by input_mt_report_pointer_emulation() later, but not report it as
part of MT packet.

-- 
Dmitry