Input: add AD7879 Touchscreen driver

[randy.dunlap@oracle.com: don't use bus_id]
[dtor@mail.ru: locking and other fixups]
Signed-off-by: NMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

drivers/input/touchscreen/Kconfig

@@ -42,6 +42,38 @@ config TOUCHSCREEN_AD7877
 	  To compile this driver as a module, choose M here: the
 	  module will be called ad7877.
 
+config TOUCHSCREEN_AD7879_I2C
+	tristate "AD7879 based touchscreens: AD7879-1 I2C Interface"
+	depends on I2C
+	select TOUCHSCREEN_AD7879
+	help
+	  Say Y here if you have a touchscreen interface using the
+	  AD7879-1 controller, and your board-specific initialization
+	  code includes that in its table of I2C devices.
+
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7879.
+
+config TOUCHSCREEN_AD7879_SPI
+	tristate "AD7879 based touchscreens: AD7879 SPI Interface"
+	depends on SPI_MASTER && TOUCHSCREEN_AD7879_I2C = n
+	select TOUCHSCREEN_AD7879
+	help
+	  Say Y here if you have a touchscreen interface using the
+	  AD7879 controller, and your board-specific initialization
+	  code includes that in its table of SPI devices.
+
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7879.
+
+config TOUCHSCREEN_AD7879
+	tristate
+	default n
+
 config TOUCHSCREEN_BITSY
 	tristate "Compaq iPAQ H3600 (Bitsy) touchscreen"
 	depends on SA1100_BITSY

drivers/input/touchscreen/Makefile

@@ -7,6 +7,7 @@
 wm97xx-ts-y := wm97xx-core.o
 
 obj-$(CONFIG_TOUCHSCREEN_AD7877)	+= ad7877.o
+obj-$(CONFIG_TOUCHSCREEN_AD7879)	+= ad7879.o
 obj-$(CONFIG_TOUCHSCREEN_ADS7846)	+= ads7846.o
 obj-$(CONFIG_TOUCHSCREEN_ATMEL_TSADCC)	+= atmel_tsadcc.o
 obj-$(CONFIG_TOUCHSCREEN_BITSY)		+= h3600_ts_input.o

drivers/input/touchscreen/ad7879.c

+/*
+ * Copyright (C) 2008 Michael Hennerich, Analog Devices Inc.
+ *
+ * Description:	AD7879 based touchscreen, and GPIO driver (I2C/SPI Interface)
+ *
+ * Bugs:        Enter bugs at http://blackfin.uclinux.org/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see the file COPYING, or write
+ * to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * History:
+ * Copyright (c) 2005 David Brownell
+ * Copyright (c) 2006 Nokia Corporation
+ * Various changes: Imre Deak <imre.deak@nokia.com>
+ *
+ * Using code from:
+ *  - corgi_ts.c
+ *	Copyright (C) 2004-2005 Richard Purdie
+ *  - omap_ts.[hc], ads7846.h, ts_osk.c
+ *	Copyright (C) 2002 MontaVista Software
+ *	Copyright (C) 2004 Texas Instruments
+ *	Copyright (C) 2005 Dirk Behme
+ *  - ad7877.c
+ *	Copyright (C) 2006-2008 Analog Devices Inc.
+ */
+
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/spi/spi.h>
+#include <linux/i2c.h>
+
+#include <linux/spi/ad7879.h>
+
+#define AD7879_REG_ZEROS		0
+#define AD7879_REG_CTRL1		1
+#define AD7879_REG_CTRL2		2
+#define AD7879_REG_CTRL3		3
+#define AD7879_REG_AUX1HIGH		4
+#define AD7879_REG_AUX1LOW		5
+#define AD7879_REG_TEMP1HIGH		6
+#define AD7879_REG_TEMP1LOW		7
+#define AD7879_REG_XPLUS		8
+#define AD7879_REG_YPLUS		9
+#define AD7879_REG_Z1			10
+#define AD7879_REG_Z2			11
+#define AD7879_REG_AUXVBAT		12
+#define AD7879_REG_TEMP			13
+#define AD7879_REG_REVID		14
+
+/* Control REG 1 */
+#define AD7879_TMR(x)			((x & 0xFF) << 0)
+#define AD7879_ACQ(x)			((x & 0x3) << 8)
+#define AD7879_MODE_NOC			(0 << 10)	/* Do not convert */
+#define AD7879_MODE_SCC			(1 << 10)	/* Single channel conversion */
+#define AD7879_MODE_SEQ0		(2 << 10)	/* Sequence 0 in Slave Mode */
+#define AD7879_MODE_SEQ1		(3 << 10)	/* Sequence 1 in Master Mode */
+#define AD7879_MODE_INT			(1 << 15)	/* PENIRQ disabled INT enabled */
+
+/* Control REG 2 */
+#define AD7879_FCD(x)			((x & 0x3) << 0)
+#define AD7879_RESET			(1 << 4)
+#define AD7879_MFS(x)			((x & 0x3) << 5)
+#define AD7879_AVG(x)			((x & 0x3) << 7)
+#define	AD7879_SER			(1 << 9)	/* non-differential */
+#define	AD7879_DFR			(0 << 9)	/* differential */
+#define AD7879_GPIOPOL			(1 << 10)
+#define AD7879_GPIODIR			(1 << 11)
+#define AD7879_GPIO_DATA		(1 << 12)
+#define AD7879_GPIO_EN			(1 << 13)
+#define AD7879_PM(x)			((x & 0x3) << 14)
+#define AD7879_PM_SHUTDOWN		(0)
+#define AD7879_PM_DYN			(1)
+#define AD7879_PM_FULLON		(2)
+
+/* Control REG 3 */
+#define AD7879_TEMPMASK_BIT		(1<<15)
+#define AD7879_AUXVBATMASK_BIT		(1<<14)
+#define AD7879_INTMODE_BIT		(1<<13)
+#define AD7879_GPIOALERTMASK_BIT	(1<<12)
+#define AD7879_AUXLOW_BIT		(1<<11)
+#define AD7879_AUXHIGH_BIT		(1<<10)
+#define AD7879_TEMPLOW_BIT		(1<<9)
+#define AD7879_TEMPHIGH_BIT		(1<<8)
+#define AD7879_YPLUS_BIT		(1<<7)
+#define AD7879_XPLUS_BIT		(1<<6)
+#define AD7879_Z1_BIT			(1<<5)
+#define AD7879_Z2_BIT			(1<<4)
+#define AD7879_AUX_BIT			(1<<3)
+#define AD7879_VBAT_BIT			(1<<2)
+#define AD7879_TEMP_BIT			(1<<1)
+
+enum {
+	AD7879_SEQ_XPOS  = 0,
+	AD7879_SEQ_YPOS  = 1,
+	AD7879_SEQ_Z1    = 2,
+	AD7879_SEQ_Z2    = 3,
+	AD7879_NR_SENSE  = 4,
+};
+
+#define	MAX_12BIT			((1<<12)-1)
+#define	TS_PEN_UP_TIMEOUT		msecs_to_jiffies(50)
+
+#if defined(CONFIG_TOUCHSCREEN_AD7879_SPI) || defined(CONFIG_TOUCHSCREEN_AD7879_SPI_MODULE)
+#define AD7879_DEVID		0x7A
+typedef struct spi_device	bus_device;
+#elif defined(CONFIG_TOUCHSCREEN_AD7879_I2C) || defined(CONFIG_TOUCHSCREEN_AD7879_I2C_MODULE)
+#define AD7879_DEVID		0x79
+typedef struct i2c_client	bus_device;
+#endif
+
+struct ad7879 {
+	bus_device		*bus;
+	struct input_dev	*input;
+	struct work_struct	work;
+	struct timer_list	timer;
+
+	struct mutex		mutex;
+	unsigned		disabled:1;	/* P: mutex */
+
+#if defined(CONFIG_TOUCHSCREEN_AD7879_SPI) || defined(CONFIG_TOUCHSCREEN_AD7879_SPI_MODULE)
+	struct spi_message	msg;
+	struct spi_transfer	xfer[AD7879_NR_SENSE + 1];
+	u16			cmd;
+#endif
+	u16			conversion_data[AD7879_NR_SENSE];
+	char			phys[32];
+	u8			first_conversion_delay;
+	u8			acquisition_time;
+	u8			averaging;
+	u8			pen_down_acc_interval;
+	u8			median;
+	u16			x_plate_ohms;
+	u16			pressure_max;
+	u16			gpio_init;
+	u16			cmd_crtl1;
+	u16			cmd_crtl2;
+	u16			cmd_crtl3;
+	unsigned		gpio:1;
+};
+
+static int ad7879_read(bus_device *, u8);
+static int ad7879_write(bus_device *, u8, u16);
+static void ad7879_collect(struct ad7879 *);
+
+static void ad7879_report(struct ad7879 *ts)
+{
+	struct input_dev *input_dev = ts->input;
+	unsigned Rt;
+	u16 x, y, z1, z2;
+
+	x = ts->conversion_data[AD7879_SEQ_XPOS] & MAX_12BIT;
+	y = ts->conversion_data[AD7879_SEQ_YPOS] & MAX_12BIT;
+	z1 = ts->conversion_data[AD7879_SEQ_Z1] & MAX_12BIT;
+	z2 = ts->conversion_data[AD7879_SEQ_Z2] & MAX_12BIT;
+
+	/*
+	 * The samples processed here are already preprocessed by the AD7879.
+	 * The preprocessing function consists of a median and an averaging filter.
+	 * The combination of these two techniques provides a robust solution,
+	 * discarding the spurious noise in the signal and keeping only the data of interest.
+	 * The size of both filters is programmable. (dev.platform_data, see linux/spi/ad7879.h)
+	 * Other user-programmable conversion controls include variable acquisition time,
+	 * and first conversion delay. Up to 16 averages can be taken per conversion.
+	 */
+
+	if (likely(x && z1)) {
+		/* compute touch pressure resistance using equation #1 */
+		Rt = (z2 - z1) * x * ts->x_plate_ohms;
+		Rt /= z1;
+		Rt = (Rt + 2047) >> 12;
+
+		input_report_abs(input_dev, ABS_X, x);
+		input_report_abs(input_dev, ABS_Y, y);
+		input_report_abs(input_dev, ABS_PRESSURE, Rt);
+		input_sync(input_dev);
+	}
+}
+
+static void ad7879_work(struct work_struct *work)
+{
+	struct ad7879 *ts = container_of(work, struct ad7879, work);
+
+	/* use keventd context to read the result registers */
+	ad7879_collect(ts);
+	ad7879_report(ts);
+	mod_timer(&ts->timer, jiffies + TS_PEN_UP_TIMEOUT);
+}
+
+static void ad7879_ts_event_release(struct ad7879 *ts)
+{
+	struct input_dev *input_dev = ts->input;
+
+	input_report_abs(input_dev, ABS_PRESSURE, 0);
+	input_sync(input_dev);
+}
+
+static void ad7879_timer(unsigned long handle)
+{
+	struct ad7879 *ts = (void *)handle;
+
+	ad7879_ts_event_release(ts);
+}
+
+static irqreturn_t ad7879_irq(int irq, void *handle)
+{
+	struct ad7879 *ts = handle;
+
+	/* The repeated conversion sequencer controlled by TMR kicked off too fast.
+	 * We ignore the last and process the sample sequence currently in the queue.
+	 * It can't be older than 9.4ms
+	 */
+
+	if (!work_pending(&ts->work))
+		schedule_work(&ts->work);
+
+	return IRQ_HANDLED;
+}
+
+static void ad7879_setup(struct ad7879 *ts)
+{
+	ts->cmd_crtl3 = AD7879_YPLUS_BIT |
+			AD7879_XPLUS_BIT |
+			AD7879_Z2_BIT |
+			AD7879_Z1_BIT |
+			AD7879_TEMPMASK_BIT |
+			AD7879_AUXVBATMASK_BIT |
+			AD7879_GPIOALERTMASK_BIT;
+
+	ts->cmd_crtl2 = AD7879_PM(AD7879_PM_DYN) | AD7879_DFR |
+			AD7879_AVG(ts->averaging) |
+			AD7879_MFS(ts->median) |
+			AD7879_FCD(ts->first_conversion_delay) |
+			ts->gpio_init;
+
+	ts->cmd_crtl1 = AD7879_MODE_INT | AD7879_MODE_SEQ1 |
+			AD7879_ACQ(ts->acquisition_time) |
+			AD7879_TMR(ts->pen_down_acc_interval);
+
+	ad7879_write(ts->bus, AD7879_REG_CTRL2, ts->cmd_crtl2);
+	ad7879_write(ts->bus, AD7879_REG_CTRL3, ts->cmd_crtl3);
+	ad7879_write(ts->bus, AD7879_REG_CTRL1, ts->cmd_crtl1);
+}
+
+static void ad7879_disable(struct ad7879 *ts)
+{
+	mutex_lock(&ts->mutex);
+
+	if (!ts->disabled) {
+
+		ts->disabled = 1;
+		disable_irq(ts->bus->irq);
+
+		cancel_work_sync(&ts->work);
+
+		if (del_timer_sync(&ts->timer))
+			ad7879_ts_event_release(ts);
+
+		ad7879_write(ts->bus, AD7879_REG_CTRL2,
+			     AD7879_PM(AD7879_PM_SHUTDOWN));
+	}
+
+	mutex_unlock(&ts->mutex);
+}
+
+static void ad7879_enable(struct ad7879 *ts)
+{
+	mutex_lock(&ts->mutex);
+
+	if (ts->disabled) {
+		ad7879_setup(ts);
+		ts->disabled = 0;
+		enable_irq(ts->bus->irq);
+	}
+
+	mutex_unlock(&ts->mutex);
+}
+
+static ssize_t ad7879_disable_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct ad7879 *ts = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", ts->disabled);
+}
+
+static ssize_t ad7879_disable_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct ad7879 *ts = dev_get_drvdata(dev);
+	unsigned long val;
+	int error;
+
+	error = strict_strtoul(buf, 10, &val);
+	if (error)
+		return error;
+
+	if (val)
+		ad7879_disable(ts);
+	else
+		ad7879_enable(ts);
+
+	return count;
+}
+
+static DEVICE_ATTR(disable, 0664, ad7879_disable_show, ad7879_disable_store);
+
+static ssize_t ad7879_gpio_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct ad7879 *ts = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", ts->gpio);
+}
+
+static ssize_t ad7879_gpio_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct ad7879 *ts = dev_get_drvdata(dev);
+	unsigned long val;
+	int error;
+
+	error = strict_strtoul(buf, 10, &val);
+	if (error)
+		return error;
+
+	mutex_lock(&ts->mutex);
+	ts->gpio = !!val;
+	error = ad7879_write(ts->bus, AD7879_REG_CTRL2,
+			   ts->gpio ?
+				ts->cmd_crtl2 & ~AD7879_GPIO_DATA :
+				ts->cmd_crtl2 | AD7879_GPIO_DATA);
+	mutex_unlock(&ts->mutex);
+
+	return error ? : count;
+}
+
+static DEVICE_ATTR(gpio, 0664, ad7879_gpio_show, ad7879_gpio_store);
+
+static struct attribute *ad7879_attributes[] = {
+	&dev_attr_disable.attr,
+	&dev_attr_gpio.attr,
+	NULL
+};
+
+static const struct attribute_group ad7879_attr_group = {
+	.attrs = ad7879_attributes,
+};
+
+static int __devinit ad7879_construct(bus_device *bus, struct ad7879 *ts)
+{
+	struct input_dev *input_dev;
+	struct ad7879_platform_data *pdata = bus->dev.platform_data;
+	int err;
+	u16 revid;
+
+	if (!bus->irq) {
+		dev_err(&bus->dev, "no IRQ?\n");
+		return -ENODEV;
+	}
+
+	if (!pdata) {
+		dev_err(&bus->dev, "no platform data?\n");
+		return -ENODEV;
+	}
+
+	input_dev = input_allocate_device();
+	if (!input_dev)
+		return -ENOMEM;
+
+	ts->input = input_dev;
+
+	setup_timer(&ts->timer, ad7879_timer, (unsigned long) ts);
+	INIT_WORK(&ts->work, ad7879_work);
+	mutex_init(&ts->mutex);
+
+	ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
+	ts->pressure_max = pdata->pressure_max ? : ~0;
+
+	ts->first_conversion_delay = pdata->first_conversion_delay;
+	ts->acquisition_time = pdata->acquisition_time;
+	ts->averaging = pdata->averaging;
+	ts->pen_down_acc_interval = pdata->pen_down_acc_interval;
+	ts->median = pdata->median;
+
+	if (pdata->gpio_output)
+		ts->gpio_init = AD7879_GPIO_EN |
+				(pdata->gpio_default ? 0 : AD7879_GPIO_DATA);
+	else
+		ts->gpio_init = AD7879_GPIO_EN | AD7879_GPIODIR;
+
+	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&bus->dev));
+
+	input_dev->name = "AD7879 Touchscreen";
+	input_dev->phys = ts->phys;
+	input_dev->dev.parent = &bus->dev;
+
+	__set_bit(EV_ABS, input_dev->evbit);
+	__set_bit(ABS_X, input_dev->absbit);
+	__set_bit(ABS_Y, input_dev->absbit);
+	__set_bit(ABS_PRESSURE, input_dev->absbit);
+
+	input_set_abs_params(input_dev, ABS_X,
+			pdata->x_min ? : 0,
+			pdata->x_max ? : MAX_12BIT,
+			0, 0);
+	input_set_abs_params(input_dev, ABS_Y,
+			pdata->y_min ? : 0,
+			pdata->y_max ? : MAX_12BIT,
+			0, 0);
+	input_set_abs_params(input_dev, ABS_PRESSURE,
+			pdata->pressure_min, pdata->pressure_max, 0, 0);
+
+	err = ad7879_write(bus, AD7879_REG_CTRL2, AD7879_RESET);
+
+	if (err < 0) {
+		dev_err(&bus->dev, "Failed to write %s\n", input_dev->name);
+		goto err_free_mem;
+	}
+
+	revid = ad7879_read(bus, AD7879_REG_REVID);
+
+	if ((revid & 0xFF) != AD7879_DEVID) {
+		dev_err(&bus->dev, "Failed to probe %s\n", input_dev->name);
+		err = -ENODEV;
+		goto err_free_mem;
+	}
+
+	ad7879_setup(ts);
+
+	err = request_irq(bus->irq, ad7879_irq,
+			  IRQF_TRIGGER_FALLING | IRQF_SAMPLE_RANDOM,
+			  bus->dev.driver->name, ts);
+
+	if (err) {
+		dev_err(&bus->dev, "irq %d busy?\n", bus->irq);
+		goto err_free_mem;
+	}
+
+	err = sysfs_create_group(&bus->dev.kobj, &ad7879_attr_group);
+	if (err)
+		goto err_free_irq;
+
+	err = input_register_device(input_dev);
+	if (err)
+		goto err_remove_attr;
+
+	dev_info(&bus->dev, "Rev.%d touchscreen, irq %d\n",
+		 revid >> 8, bus->irq);
+
+	return 0;
+
+err_remove_attr:
+	sysfs_remove_group(&bus->dev.kobj, &ad7879_attr_group);
+err_free_irq:
+	free_irq(bus->irq, ts);
+err_free_mem:
+	input_free_device(input_dev);
+
+	return err;
+}
+
+static int __devexit ad7879_destroy(bus_device *bus, struct ad7879 *ts)
+{
+	ad7879_disable(ts);
+	sysfs_remove_group(&ts->bus->dev.kobj, &ad7879_attr_group);
+	free_irq(ts->bus->irq, ts);
+	input_unregister_device(ts->input);
+	dev_dbg(&bus->dev, "unregistered touchscreen\n");
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int ad7879_suspend(bus_device *bus, pm_message_t message)
+{
+	struct ad7879 *ts = dev_get_drvdata(&bus->dev);
+
+	ad7879_disable(ts);
+
+	return 0;
+}
+
+static int ad7879_resume(bus_device *bus)
+{
+	struct ad7879 *ts = dev_get_drvdata(&bus->dev);
+
+	ad7879_enable(ts);
+
+	return 0;
+}
+#else
+#define ad7879_suspend NULL
+#define ad7879_resume  NULL
+#endif
+
+#if defined(CONFIG_TOUCHSCREEN_AD7879_SPI) || defined(CONFIG_TOUCHSCREEN_AD7879_SPI_MODULE)
+#define MAX_SPI_FREQ_HZ		5000000
+#define AD7879_CMD_MAGIC	0xE000
+#define AD7879_CMD_READ		(1 << 10)
+#define AD7879_WRITECMD(reg)	(AD7879_CMD_MAGIC | (reg & 0xF))
+#define AD7879_READCMD(reg)	(AD7879_CMD_MAGIC | AD7879_CMD_READ | (reg & 0xF))
+
+struct ser_req {
+	u16			command;
+	u16			data;
+	struct spi_message	msg;
+	struct spi_transfer	xfer[2];
+};
+
+/*
+ * ad7879_read/write are only used for initial setup and for sysfs controls.
+ * The main traffic is done in ad7879_collect().
+ */
+
+static int ad7879_read(struct spi_device *spi, u8 reg)
+{
+	struct ser_req *req;
+	int status, ret;
+
+	req = kzalloc(sizeof *req, GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	spi_message_init(&req->msg);
+
+	req->command = (u16) AD7879_READCMD(reg);
+	req->xfer[0].tx_buf = &req->command;
+	req->xfer[0].len = 2;
+
+	req->xfer[1].rx_buf = &req->data;
+	req->xfer[1].len = 2;
+
+	spi_message_add_tail(&req->xfer[0], &req->msg);
+	spi_message_add_tail(&req->xfer[1], &req->msg);
+
+	status = spi_sync(spi, &req->msg);
+	ret = status ? : req->data;
+
+	kfree(req);
+
+	return ret;
+}
+
+static int ad7879_write(struct spi_device *spi, u8 reg, u16 val)
+{
+	struct ser_req *req;
+	int status;
+
+	req = kzalloc(sizeof *req, GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	spi_message_init(&req->msg);
+
+	req->command = (u16) AD7879_WRITECMD(reg);
+	req->xfer[0].tx_buf = &req->command;
+	req->xfer[0].len = 2;
+
+	req->data = val;
+	req->xfer[1].tx_buf = &req->data;
+	req->xfer[1].len = 2;
+
+	spi_message_add_tail(&req->xfer[0], &req->msg);
+	spi_message_add_tail(&req->xfer[1], &req->msg);
+
+	status = spi_sync(spi, &req->msg);
+
+	kfree(req);
+
+	return status;
+}
+
+static void ad7879_collect(struct ad7879 *ts)
+{
+	int status = spi_sync(ts->bus, &ts->msg);
+
+	if (status)
+		dev_err(&ts->bus->dev, "spi_sync --> %d\n", status);
+}
+
+static void ad7879_setup_ts_def_msg(struct ad7879 *ts)
+{
+	struct spi_message *m;
+	int i;
+
+	ts->cmd = (u16) AD7879_READCMD(AD7879_REG_XPLUS);
+
+	m = &ts->msg;
+	spi_message_init(m);
+	ts->xfer[0].tx_buf = &ts->cmd;
+	ts->xfer[0].len = 2;
+
+	spi_message_add_tail(&ts->xfer[0], m);
+
+	for (i = 0; i < AD7879_NR_SENSE; i++) {
+		ts->xfer[i + 1].rx_buf = &ts->conversion_data[i];
+		ts->xfer[i + 1].len = 2;
+		spi_message_add_tail(&ts->xfer[i + 1], m);
+	}
+}
+
+static int __devinit ad7879_probe(struct spi_device *spi)
+{
+	struct ad7879 *ts;
+	int error;
+
+	/* don't exceed max specified SPI CLK frequency */
+	if (spi->max_speed_hz > MAX_SPI_FREQ_HZ) {
+		dev_err(&spi->dev, "SPI CLK %d Hz?\n", spi->max_speed_hz);
+		return -EINVAL;
+	}
+
+	ts = kzalloc(sizeof(struct ad7879), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	dev_set_drvdata(&spi->dev, ts);
+	ts->bus = spi;
+
+	ad7879_setup_ts_def_msg(ts);
+
+	error = ad7879_construct(spi, ts);
+	if (error) {
+		dev_set_drvdata(&spi->dev, NULL);
+		kfree(ts);
+	}
+
+	return 0;
+}
+
+static int __devexit ad7879_remove(struct spi_device *spi)
+{
+	struct ad7879 *ts = dev_get_drvdata(&spi->dev);
+
+	ad7879_destroy(spi, ts);
+	dev_set_drvdata(&spi->dev, NULL);
+	kfree(ts);
+
+	return 0;
+}
+
+static struct spi_driver ad7879_driver = {
+	.driver = {
+		.name	= "ad7879",
+		.bus	= &spi_bus_type,
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ad7879_probe,
+	.remove		= __devexit_p(ad7879_remove),
+	.suspend	= ad7879_suspend,
+	.resume		= ad7879_resume,
+};
+
+static int __init ad7879_init(void)
+{
+	return spi_register_driver(&ad7879_driver);
+}
+module_init(ad7879_init);
+
+static void __exit ad7879_exit(void)
+{
+	spi_unregister_driver(&ad7879_driver);
+}
+module_exit(ad7879_exit);
+
+#elif defined(CONFIG_TOUCHSCREEN_AD7879_I2C) || defined(CONFIG_TOUCHSCREEN_AD7879_I2C_MODULE)
+
+/* All registers are word-sized.
+ * AD7879 uses a high-byte first convention.
+ */
+static int ad7879_read(struct i2c_client *client, u8 reg)
+{
+	return swab16(i2c_smbus_read_word_data(client, reg));
+}
+
+static int ad7879_write(struct i2c_client *client, u8 reg, u16 val)
+{
+	return i2c_smbus_write_word_data(client, reg, swab16(val));
+}
+
+static void ad7879_collect(struct ad7879 *ts)
+{
+	int i;
+
+	for (i = 0; i < AD7879_NR_SENSE; i++)
+		ts->conversion_data[i] = ad7879_read(ts->bus,
+						     AD7879_REG_XPLUS + i);
+}
+
+static int __devinit ad7879_probe(struct i2c_client *client,
+					const struct i2c_device_id *id)
+{
+	struct ad7879 *ts;
+	int error;
+
+	if (!i2c_check_functionality(client->adapter,
+					I2C_FUNC_SMBUS_WORD_DATA)) {
+		dev_err(&client->dev, "SMBUS Word Data not Supported\n");
+		return -EIO;
+	}
+
+	ts = kzalloc(sizeof(struct ad7879), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, ts);
+	ts->bus = client;
+
+	error = ad7879_construct(client, ts);
+	if (error) {
+		i2c_set_clientdata(client, NULL);
+		kfree(ts);
+	}
+
+	return 0;
+}
+
+static int __devexit ad7879_remove(struct i2c_client *client)
+{
+	struct ad7879 *ts = dev_get_drvdata(&client->dev);
+
+	ad7879_destroy(client, ts);
+	i2c_set_clientdata(client, NULL);
+	kfree(ts);
+
+	return 0;
+}
+
+static const struct i2c_device_id ad7879_id[] = {
+	{ "ad7879", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ad7879_id);
+
+static struct i2c_driver ad7879_driver = {
+	.driver = {
+		.name	= "ad7879",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ad7879_probe,
+	.remove		= __devexit_p(ad7879_remove),
+	.suspend	= ad7879_suspend,
+	.resume		= ad7879_resume,
+	.id_table	= ad7879_id,
+};
+
+static int __init ad7879_init(void)
+{
+	return i2c_add_driver(&ad7879_driver);
+}
+module_init(ad7879_init);
+
+static void __exit ad7879_exit(void)
+{
+	i2c_del_driver(&ad7879_driver);
+}
+module_exit(ad7879_exit);
+#endif
+
+MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>");
+MODULE_DESCRIPTION("AD7879(-1) touchscreen Driver");
+MODULE_LICENSE("GPL");

include/linux/spi/ad7879.h

+/* linux/spi/ad7879.h */
+
+/* Touchscreen characteristics vary between boards and models.  The
+ * platform_data for the device's "struct device" holds this information.
+ *
+ * It's OK if the min/max values are zero.
+ */
+struct ad7879_platform_data {
+	u16	model;			/* 7879 */
+	u16	x_plate_ohms;
+	u16	x_min, x_max;
+	u16	y_min, y_max;
+	u16	pressure_min, pressure_max;
+
+	/* [0..255] 0=OFF Starts at 1=550us and goes
+	 * all the way to 9.440ms in steps of 35us.
+	 */
+	u8	pen_down_acc_interval;
+	/* [0..15] Starts at 0=128us and goes all the
+	 * way to 4.096ms in steps of 128us.
+	 */
+	u8	first_conversion_delay;
+	/* [0..3] 0 = 2us, 1 = 4us, 2 = 8us, 3 = 16us */
+	u8	acquisition_time;
+	/* [0..3] Average X middle samples 0 = 2, 1 = 4, 2 = 8, 3 = 16 */
+	u8	averaging;
+	/* [0..3] Perform X measurements 0 = OFF,
+	 * 1 = 4, 2 = 8, 3 = 16 (median > averaging)
+	 */
+	u8	median;
+	/* 1 = AUX/VBAT/GPIO set to GPIO Output */
+	u8	gpio_output;
+	/* Initial GPIO pin state (valid if gpio_output = 1) */
+	u8	gpio_default;
+};