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Subject[PATCH] usb: generic calibration support
Date
From: Holger Schurig <hs4233@mail.mn-solutions.de>

Generic calibration support for usbtouchscreen.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>

---

With build-in calibration support, the "swap_xy" kernel parameter
vanishes and usbtouchscreen instead gains a new kernel-parameter
which holds 7 integers.

This is used to calibrate the resulting output of the driver. Let
x_o and y_o be the original x,y coordinate, as reported from the
device. Then x_r,y_r (the x,y coordinate reported to the input event
subsystem) are:

x_r = ( a*x_o + b*y_o + c ) / s
y_r = ( c*x_o + d*y_o + e ) / s

The default values for (a,b,c,d,e,s) are (1,0,0,0,1,0,1). To
simulate swap_xy, one would set them to (0,1,0,1,0,0,1). Once can
also use swap_x or swap_y alone, or define other, linear
transpositions. The algorithm used is the same as in Qt/Embedded
3.x for the QWSCalibratedMouseHandler.

This interface allows re-calibration at runtime, without
restarting the X-Server or any other event consumer.


Please review this patch and schedule it for inclusion once
2.6.19 comes out.


--- linux.orig/drivers/usb/input/Kconfig
+++ linux/drivers/usb/input/Kconfig
@@ -219,6 +219,32 @@
To compile this driver as a module, choose M here: the
module will be called usbtouchscreen.

+config USB_TOUCHSCREEN_CALIBRATE
+ default n
+ bool "Calibration support"
+ depends on USB_TOUCHSCREEN
+ ---help---
+ With build-in calibration support, the "swap_xy" kernel parameter
+ vanishes and usbtouchscreen instead gains a new kernel-parameter
+ which hold 7 integers. You can also access this with cat/echo
+ via /sys/module/usbtouchscreen/parameters/calibration
+
+ This is used to calibrate the resulting output of the driver. Let
+ x_o and y_o be the original x,y coordinate, as reported from the
+ device. Then x_r,y_r (the x,y coordinate reported to the input event
+ subsystem) are:
+
+ x_r = ( a*x_o + b*y_o + c ) / s
+ y_r = ( c*x_o + d*y_o + e ) / s
+
+ The default values for (a,b,c,d,e,s) are (1,0,0,0,1,0,1). To
+ simulate swap_xy, one would set them to (0,1,0,1,0,0,1).
+
+ This interface allows re-calibration at runtime, without
+ restarting the X-Server or any other event consumer.
+
+ If unsure, say N.
+
config USB_TOUCHSCREEN_DMC_TSC10
default y
bool "DMC TSC-10 device support" if EMBEDDED
--- linux.orig/drivers/usb/input/usbtouchscreen.c
+++ linux/drivers/usb/input/usbtouchscreen.c
@@ -49,9 +49,16 @@
#define DRIVER_AUTHOR "Daniel Ritz <daniel.ritz@gmx.ch>"
#define DRIVER_DESC "USB Touchscreen Driver"

+#ifdef CONFIG_USB_TOUCHSCREEN_CALIBRATE
+static int cal[7] = {1, 0, 0, 0, 1, 0, 1 };
+module_param_array_named(calibration, cal, int, NULL, 0644);
+MODULE_PARM_DESC(calibrate, "calibration data");
+
+#else
static int swap_xy;
module_param(swap_xy, bool, 0644);
MODULE_PARM_DESC(swap_xy, "If set X and Y axes are swapped.");
+#endif

/* device specifc data/functions */
struct usbtouch_usb;
@@ -499,6 +506,12 @@

input_report_key(usbtouch->input, BTN_TOUCH, touch);

+#ifdef CONFIG_USB_TOUCHSCREEN_CALIBRATE
+ if (cal[6]==0)
+ cal[6] = 1;
+ input_report_abs(usbtouch->input, ABS_X, (cal[0]*x + cal[1]*y + cal[2])/cal[6] );
+ input_report_abs(usbtouch->input, ABS_Y, (cal[3]*x + cal[4]*y + cal[5])/cal[6] );
+#else
if (swap_xy) {
input_report_abs(usbtouch->input, ABS_X, y);
input_report_abs(usbtouch->input, ABS_Y, x);
@@ -506,6 +519,7 @@
input_report_abs(usbtouch->input, ABS_X, x);
input_report_abs(usbtouch->input, ABS_Y, y);
}
+#endif
if (type->max_press)
input_report_abs(usbtouch->input, ABS_PRESSURE, press);
input_sync(usbtouch->input);
--
M&N Solutions GmbH
Holger Schurig
Dieselstr. 18
61191 Rosbach
06003/9141-15
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