[PATCH 9/9] iio: mma8452: add support for self test.

[Martin Fuzzey <mfuzzey@parkeon.com>]

Add a new attribute to activate the self test mode.

When self test is activated, an electrostatic actuation force is
applied to the sensor, simulating a small acceleration.

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
---
 .../ABI/testing/sysfs-bus-iio-accel-mma8452        |   10 ++++
 drivers/iio/accel/mma8452.c                        |   52 ++++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-accel-mma8452

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-accel-mma8452 b/Documentation/ABI/testing/sysfs-bus-iio-accel-mma8452
new file mode 100644
index 0000000..387ed38
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-accel-mma8452
@@ -0,0 +1,10 @@
+What:		/sys/bus/iio/devices/iio:deviceX/self_test
+KernelVersion:	3.21
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Allow self test mode to be controlled:
+			"0" = inactive
+			"1" = active
+		When self test is activated, an electrostatic actuation force is
+		applied to the sensor, simulating a small acceleration.
+
diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
index 6277b5d..75dcc6e 100644
--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -49,6 +49,7 @@
 #define MMA8452_CTRL_REG1 0x2a
 #define MMA8452_CTRL_REG2 0x2b
 #define MMA8452_CTRL_REG2_RST		BIT(6)
+#define MMA8452_CTRL_REG2_SELFTEST	BIT(7)
 #define MMA8452_CTRL_REG4 0x2d
 #define MMA8452_CTRL_REG5 0x2e
 
@@ -639,6 +640,56 @@ static int mma8452_reg_access_dbg(struct iio_dev *indio_dev,
 	return ret;
 }
 
+static ssize_t mma8452_show_selftest(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mma8452_data *data = iio_priv(indio_dev);
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(data->client, MMA8452_CTRL_REG2);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%d\n", ret & MMA8452_CTRL_REG2_SELFTEST ? 1 : 0);
+}
+
+static ssize_t mma8452_store_selftest(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mma8452_data *data = iio_priv(indio_dev);
+	bool state;
+	int ret;
+	u8 val;
+
+	ret = strtobool(buf, &state);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_byte_data(data->client, MMA8452_CTRL_REG2);
+	if (ret < 0)
+		return ret;
+
+	val = ret;
+	if (state)
+		val |= MMA8452_CTRL_REG2_SELFTEST;
+	else
+		val &= ~MMA8452_CTRL_REG2_SELFTEST;
+
+	ret = mma8452_change_config(data, MMA8452_CTRL_REG2, val);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(self_test,
+			 S_IRUGO | S_IWUSR,
+			 mma8452_show_selftest,
+			 mma8452_store_selftest, 0);
+
 static const struct iio_event_spec mma8452_transient_event[] = {
 	{
 		.type = IIO_EV_TYPE_THRESH,
@@ -698,6 +749,7 @@ static struct attribute *mma8452_attributes[] = {
 	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
 	&iio_dev_attr_in_accel_scale_available.dev_attr.attr,
 	&iio_dev_attr_in_accel_filter_high_pass_3db_frequency_available.dev_attr.attr,
+	&iio_dev_attr_self_test.dev_attr.attr,
 	NULL
 };