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

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Date:   Thu, 18 Oct 2018 10:39:39 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>, robh@...nel.org
Cc:     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

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

Also the touchscreen bindings have: touchscreen-x-mm and touchscreen-y-mm
rather then res, which can then be used to calculate the resolution.

Regards,

Hans