Hi,

Am 24.09.2016 um 00:47 schrieb Rob Herring [off-list ref]:

On Fri, Sep 23, 2016 at 02:41:09PM +0200, H. Nikolaus Schaller wrote:

quoted

commit b98abe52fa8e ("Input: add common DT binding for touchscreens")
introduced common DT bindings for touchscreens [1] and a helper function to
parse the DT.

commit ed7c9870c9bc ("Input: of_touchscreen - add support for inverted / swapped axes")
added another helper for parsing axis inversion and swapping
and applying them to x and y coordinates.

Both helpers have been integrated to accommodate any orientation of the
touch panel in relation to the LCD.

A new feature is to introduce scaling the min/max ADC values to the screen
size.

This makes it possible to pre-calibrate the touch so that is (almost)
exactly matches the LCD pixel coordinates it is glued onto. This allows to
well enough operate the touch before a user space calibration step can
improve the precision.

Finally, calculate_pressure has been renamed to calculate_resistance
because that is what it is doing.

Seems like you are breaking compatibility with old DTs. I can't tell for 
sure though.

There is code to take missing values as 0 or maximum. So this will scale 1:1
and should not break old DTs.

quoted

[1]: Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

Signed-off-by: H. Nikolaus Schaller <redacted>
---
.../bindings/input/touchscreen/tsc2007.txt         |  20 ++--
drivers/input/touchscreen/tsc2007.c                | 126 +++++++++++++++++----
include/linux/i2c/tsc2007.h                        |   8 ++
3 files changed, 123 insertions(+), 31 deletions(-)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt b/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt
index ec365e1..6e9fd55 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt

@@ -6,6 +6,7 @@ Required properties:
- ti,x-plate-ohms: X-plate resistance in ohms.

Optional properties:
+- generic touch screen properties: see touchscreen binding [2].
- gpios: the interrupt gpio the chip is connected to (trough the penirq pin).
  The penirq pin goes to low when the panel is touched.
  (see GPIO binding[1] for more details).

@@ -13,17 +14,20 @@ Optional properties:
  (see interrupt binding[0]).
- interrupts: (gpio) interrupt to which the chip is connected
  (see interrupt binding[0]).
-- ti,max-rt: maximum pressure.
-- ti,fuzzx: specifies the absolute input fuzz x value.
-  If set, it will permit noise in the data up to +- the value given to the fuzz
-  parameter, that is used to filter noise from the event stream.
-- ti,fuzzy: specifies the absolute input fuzz y value.
-- ti,fuzzz: specifies the absolute input fuzz z value.
+- ti,max-rt: maximum pressure resistance above which samples are ignored
+  (default: 4095).
+- ti,report-resistance: report resistance (no pressure = max_rt) instead
+  of pressure (no pressure = 0).
+- ti,min-x: minimum value reported by X axis ADC (default 0).
+- ti,max-x: maximum value reported by X axis ADC (default 4095).
+- ti,min-y: minimum value reported by Y axis ADC (default 0).
+- ti,max-y: maximum value reported by Y axis ADC (default 4095).

Seems like these could be common too. They make more sense than giving x 
and y sizes in pixel units which really should come from the panel.

No. They have a different purpose!

You need to scale values like this:

ti,min-x   ->   0
x          ->   some value between 0 and touchscreen-size-x
ti,max-x   ->   touchscreen-size-x

So the ti, values describe the ADC raw values while the common bindings
describe the size in input-event coordinates.

So we need both specified: raw values and pixel values.

quoted

- ti,poll-period: how much time to wait (in milliseconds) before reading again the
-  values from the tsc2007.
+  values from the tsc2007 (default 1).

[0]: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
[1]: Documentation/devicetree/bindings/gpio/gpio.txt
+[2]: Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

Example:
	&i2c1 {

@@ -35,6 +39,8 @@ Example:

			interrupts = <0x0 0x8>;
			gpios = <&gpio4 0 0>;
			ti,x-plate-ohms = <180>;
+			touchscreen-size-x = <640>;
+			touchscreen-size-y = <480>;
		};

		/* ... */

BR,
Nikolaus

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