[PATCH] iio: chemical: sps30: add support for self cleaning

[Tomasz Duszynski]

Self cleaning is especially useful in cases where sensor undergoes
frequent power on/off cycles. In such scenarios it is recommended to
turn self cleaning at least once per week in order to maintain reliable
measurements.

Self cleaning is activated by writing 1 to a dedicated attribute.
Internal fan accelerates to its maximum speed and keeps spinning
for about 10 seconds blowing out accumulated dust.

Signed-off-by: Tomasz Duszynski <tduszyns@xxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-bus-iio-sps30 |  8 +++++
 drivers/iio/chemical/sps30.c                  | 34 +++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-sps30

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-sps30 b/Documentation/ABI/testing/sysfs-bus-iio-sps30
new file mode 100644
index 000000000000..81c91f225b2d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-sps30
@@ -0,0 +1,8 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_start_cleaning
+Date:		December 2018
+KernelVersion:	4.22
+Contact:	linux-iio@xxxxxxxxxxxxxxx
+Description:
+		Writing 1 starts sensor self cleaning. Internal fan accelerates
+		to its maximum speed and keeps spinning for about 10 seconds in
+		order to blow out accumulated dust.
diff --git a/drivers/iio/chemical/sps30.c b/drivers/iio/chemical/sps30.c
index fa3cd409b90b..1cb05cfc4bba 100644
--- a/drivers/iio/chemical/sps30.c
+++ b/drivers/iio/chemical/sps30.c
@@ -37,6 +37,7 @@
 #define SPS30_READ_DATA_READY_FLAG 0x0202
 #define SPS30_READ_DATA 0x0300
 #define SPS30_READ_SERIAL 0xd033
+#define SPS30_START_FAN_CLEANING 0x5607
 
 enum {
 	PM1,
@@ -104,6 +105,7 @@ static int sps30_do_cmd(struct sps30_state *state, u16 cmd, u8 *data, int size)
 		break;
 	case SPS30_STOP_MEAS:
 	case SPS30_RESET:
+	case SPS30_START_FAN_CLEANING:
 		ret = sps30_write_then_read(state, buf, 2, NULL, 0);
 		break;
 	case SPS30_READ_DATA_READY_FLAG:
@@ -275,7 +277,39 @@ static int sps30_read_raw(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
+static ssize_t in_start_cleaning_store(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct sps30_state *state = iio_priv(indio_dev);
+	int val, ret;
+
+	if (kstrtoint(buf, 0, &val) || val != 1)
+		return -EINVAL;
+
+	mutex_lock(&state->lock);
+	ret = sps30_do_cmd(state, SPS30_START_FAN_CLEANING, NULL, 0);
+	mutex_unlock(&state->lock);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR_WO(in_start_cleaning, 0);
+
+static struct attribute *sps30_attrs[] = {
+	&iio_dev_attr_in_start_cleaning.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group sps30_attr_group = {
+	.attrs = sps30_attrs,
+};
+
 static const struct iio_info sps30_info = {
+	.attrs = &sps30_attr_group,
 	.read_raw = sps30_read_raw,
 };
 
-- 
2.20.0