linux-kernel - Re: [PATCH 3/5] dt-bindings: add more optional properties for elan

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Message-ID: <CAO-hwJKXBvuGLensAQv82SoPh-vrt9UFgoC3_XeTA78EHCOANA@mail.gmail.com>
Date:   Thu, 18 Oct 2018 10:44:16 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     robh@...nel.org, Dmitry Torokhov <dmitry.torokhov@...il.com>,
        廖崇榮 <kt.liao@....com.tw>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH 3/5] dt-bindings: add more optional properties for
 elan_i2c touchpads

On Thu, Oct 18, 2018 at 10:39 AM Hans de Goede <hdegoede@...hat.com> wrote:
>
> Hi,
>
> On 18-10-18 10:10, Benjamin Tissoires wrote:
> > On Wed, Oct 17, 2018 at 10:15 PM Rob Herring <robh@...nel.org> 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@...hat.com>
> >>> ---
> >>>   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.

> Note that for historical reasons
> Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

Looks like your sentence is not finished here :)

>
> 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.

Cheers,
Benjamin