linux-kernel - Re: [PATCH 4/8 v3] Input: synaptics

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Message-ID: <CAGS+omCeb6R_Y7Js+da=E+etNYXWu+DjT=Mio_DLSwQo97yNkg@mail.gmail.com>
Date:	Wed, 17 Aug 2011 22:05:48 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	chase.douglas@...onical.com, dmitry.torokhov@...il.com,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	olofj@...omium.org, chris@...bagwell.com
Subject: Re: [PATCH 4/8 v3] Input: synaptics - add image sensor support

On Mon, Aug 15, 2011 at 3:17 PM, Daniel Kurtz <djkurtz@...omium.org> wrote:
>
> Hi Henrik,
>
> Thanks for the great feedback.
>
> On Sat, Aug 13, 2011 at 5:09 AM, Henrik Rydberg <rydberg@...omail.se> wrote:
> > 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...
> ....
> >
> > 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.

Do you agree with this?

Thanks,
-Dan
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