[PATCH] spi: ads7846 driver
This is a driver for the ADS7846 touchscreen sensor, derived from
the corgi_ts and omap_ts drivers. Key differences from those two:
- Uses the new SPI framework (minimalist version)
- <linux/spi/ads7846.h> abstracts board-specific touchscreen info
- Sysfs attributes for the temperature and voltage sensors
- Uses fewer ARM-specific IRQ primitives
The temperature and voltage sensors show up in sysfs like this:
$ pwd
/sys/devices/platform/omap-uwire/spi2.0
$ ls
bus@ input:event0@ power/ temp1 vbatt
driver@ modalias temp0 vaux
$ cat modalias
ads7846
$ cat temp0
991
$ cat temp1
1177
$
So far only basic testing has been done. There's a fair amount of hardware
that uses this sensor, and which also runs Linux, which should eventually
be able to use this driver.
One portability note may be of special interest. It turns out that not all
SPI controllers are happy issuing requests that do things like "write 8 bit
command, read 12 bit response". Most of them seem happy to handle various
word sizes, so the issue isn't "12 bit response" but rather "different rx
and tx write sizes", despite that being a common MicroWire convention. So
this version of the driver no longer reads 12 bit native-endian words; it
reads 16-bit big-endian responses, then byteswaps them and shifts the
results to discard the noise.
Signed-off-by: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
new file mode 100644
index 0000000..84a2701
--- /dev/null
+++ b/include/linux/spi/ads7846.h
@@ -0,0 +1,18 @@
+/* linux/spi/ads7846.h */
+
+/* Touchscreen characteristics vary between boards and models. The
+ * platform_data for the device's "struct device" holts this information.
+ *
+ * It's OK if the min/max values are zero.
+ */
+struct ads7846_platform_data {
+ u16 model; /* 7843, 7845, 7846. */
+ u16 vref_delay_usecs; /* 0 for external vref; etc */
+ u16 x_plate_ohms;
+ u16 y_plate_ohms;
+
+ u16 x_min, x_max;
+ u16 y_min, y_max;
+ u16 pressure_min, pressure_max;
+};
+