Re: [PATCH 3/5] dt-bindings: add more optional properties for elan_i2c touchpads

[Hans de Goede]

Hi,

On 18-10-18 10:44, Benjamin Tissoires wrote:
> On Thu, Oct 18, 2018 at 10:39 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > Hi,
> >
> > On 18-10-18 10:10, Benjamin Tissoires wrote:
> > > On Wed, Oct 17, 2018 at 10:15 PM Rob Herring <robh@xxxxxxxxxx> wrote:
> > > > On Fri, Oct 12, 2018 at 04:24:11PM +0200, Benjamin Tissoires wrote:
> > > > > Some new touchpads IC are connected through PS/2 and I2C. On some of these
> > > > > new IC, the I2C part doesn't have all of the information available.
> > > > > We need to be able to forward the touchpad parameters from PS/2 and
> > > > > thus, we need those new optional properties.
> > > > >
> > > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1628715
> > > > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> > > > > ---
> > > > >    Documentation/devicetree/bindings/input/elan_i2c.txt | 8 ++++++++
> > > > >    1 file changed, 8 insertions(+)
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/input/elan_i2c.txt b/Documentation/devicetree/bindings/input/elan_i2c.txt
> > > > > index 797607460735..ace6bcb0b4eb 100644
> > > > > --- a/Documentation/devicetree/bindings/input/elan_i2c.txt
> > > > > +++ b/Documentation/devicetree/bindings/input/elan_i2c.txt
> > > > > @@ -13,6 +13,14 @@ Optional properties:
> > > > >      pinctrl binding [1]).
> > > > >    - vcc-supply: a phandle for the regulator supplying 3.3V power.
> > > > >    - elan,trackpoint: touchpad can support a trackpoint (boolean)
> > > > > +- elan,clickpad: touchpad is a clickpad (the entire surface is a button)
> > > >
> > > > > +- elan,max_x: the maximum reported value on the X axis
> > > > > +- elan,max_y: the maximum reported value on the Y axis
> > > > > +- elan,min_x: the minimum reported value on the X axis
> > > > > +- elan,min_y: the minimum reported value on the Y axis
> > > > > +- elan,x_res: the resolution of the X axis (in units per mm)
> > > > > +- elan,y_res: the resolution of the Y axis (in units per mm)
> > > > > +- elan,width: max reported width of a blob
> > > >
> > > > Can't we use standard touchscreen properties here? (Yes, I get this is a
> > > > touchpad, not touchscreen).
> > >
> > > Hey Rob,
> > >
> > > Well, there is that (it's a touchpad driver) and we can't also really
> > > use the of_touchscreen.c implementation.
> > > If both concerns are not an issue, we can then move the [min/max/res]
> > > properties to the touchscreen ones.
> > >
> > > Regarding 'elan,width', this is something missing from the standard ts
> > > properties, and AFAICT, this controls the maximum reported
> > > width/height of a touch.
> > > I should probably rename them to max_width, max_height.
> > >
> > > Hans, do you think we should add such properties to of_touchscreen.c
> > > too? (the width/height ones)
> >
> > Are there touchscreens which report finger/touch width / height ? if so
> > then it probably does make sense.
>
> Well, it's pretty common for hid-multitouch touchscreens to report
> such properties (it's a way to indicate the palm). Don't know about
> the touchscreens that rely on of_touchscreen though.

Now that you mention it I think some may also have some sort of
pressure/weight value, but at least for the ones I wrote I do not
think we do anything with it, since the actual meaning of the
field is somewhat vague. This is all IIRC.

> > Note that for historical reasons
> > Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
>
> Looks like your sentence is not finished here :)

I actually deleted it, but not those 2 lines, what I had written there
was that for historical reasons it uses touchscreen-size-x rather then
max-x and that that might be a bit confusing vs max-width, but I could
not come up with something better then max-width, so I deleted my
rambling, but ended up not deleting all of it :)

> > Also the touchscreen bindings have: touchscreen-x-mm and touchscreen-y-mm
> > rather then res, which can then be used to calculate the resolution.
>
> yeah, that's fine, I would need to convert to mm, then go back to res.
> Extra effort, but that's the price to pay.

Ack.

Regards,

Hans