[PATCH 1/3] input: tsc2007: Add pre-calibration, flipping and rotation

[Dr. H. Nikolaus Schaller]

Hi,

Am 15.01.2015 um 15:38 schrieb Sebastian Reichel <sre at kernel.org>:

> Hi,
> 
> On Thu, Jan 15, 2015 at 08:36:44AM +0100, Dr. H. Nikolaus Schaller wrote:
>>> 1. Perform conversion in input core rather than individual drivers. I
>>> think we should allocate a new bitmaps for some transformations and have
>>> the code do X/Y flip/clip of the coordinates.
>> 
>> Do you have a suggestion where this should be (I have no clue how
>> the input system works or is structured - we just know how to extend a
>> driver that uses it)?
>> 
>>> 2. Standardize on bindings. We already have of-touchscreen.c doing
>>> rudimentary parsing, we shoudl look into extending it rather than
>>> creating myriad of driver-specific bindings.
>> 
>> Ok, looks reasonable.
> 
> Documentation is in 
> 
> Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
> 
>>> Also, do we need swap and flip or do we simply need rotation (like the
>>> proposed Broadcom iproc driver has)?
>> 
>> Well, since the DT should describe hardware, there are 3 sets of wires which
>> can have a cross-over: X+ and X-, Y+ and Y-, X and Y.
>> 
>> So IMHO hardware has no “rotation”, just crossover of wires. Rotation is an
>> interpretation of the result of these connections in combination with some
>> panel the touch is glued to and should therefore not be represented in the DT.
>> 
>> As a result we have proposed a scheme without explicit rotation. We specify what
>> coordinates X- and X+ should report at their ends (min, max) because the DT
>> programmer has to specify them anyways. Flipping is a result of defining these
>> coordinates in an ascending or descending way. Only swapping of the X and Y
>> wires can’t be implicitly defined so it has its own property. So the scheme we
>> have proposed tries to optimize the efforts needed to adapt new boards and write
>> DTs and focus the DT on hardware description.
>> 
>> As a bonus we also specify the min and max value to be reported for the touch
>> pressure (Z axis) using the same basic principle.
>> 
>> And it is a pure add-on on top of the existing driver so that it attempts not
>> to break existing device trees.
> 
> from what I can see there are no in-tree-users using any of the
> new properties.

Not yet. But our [patch 2/3] of this series defines the DT entry for the GTA04 devices:

https://lkml.org/lkml/2014/9/30/663

> 
>> Maybe could you accept it as a first step for this specific driver (and let’s do
>> the big standardization work later on)?
> 
> That does not work, since you create an ABI.

Hm. I don’t understand what you mean with creating an ABI?