iio: Add gravity sensor support

Gravity sensor is a soft sensor, which derives value from
standard accelerometer device by filtering out the acceleration
which is not caused by gravity.

Gravity sensor provides a three dimensional vector indicating
the direction and magnitude of gravity. Typically, this sensor
is used to determine the device's relative orientation in space.
The units and the coordinate system is the same as the one used by
the acceleration sensor.
When a device is at rest, the output of the gravity sensor should
be identical to that of the accelerometer.

More information can be found in:
http://www.usb.org/developers/hidpage/HUTRR59_-_Usages_for_Wearables.pdf

Gravity sensor and accelerometer have similar channels and
share channel usage ids. So the most of the code for accel_3d
can be reused.
Signed-off-by: Song Hongyan <hongyan.song@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/hid-sensor-accel-3d.c

@@ -93,6 +93,41 @@ static const struct iio_chan_spec accel_3d_channels[] = {
 	IIO_CHAN_SOFT_TIMESTAMP(3)
 };
 
+/* Channel definitions */
+static const struct iio_chan_spec gravity_channels[] = {
+	{
+		.type = IIO_GRAVITY,
+		.modified = 1,
+		.channel2 = IIO_MOD_X,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |
+		BIT(IIO_CHAN_INFO_SCALE) |
+		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+		BIT(IIO_CHAN_INFO_HYSTERESIS),
+		.scan_index = CHANNEL_SCAN_INDEX_X,
+	}, {
+		.type = IIO_GRAVITY,
+		.modified = 1,
+		.channel2 = IIO_MOD_Y,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |
+		BIT(IIO_CHAN_INFO_SCALE) |
+		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+		BIT(IIO_CHAN_INFO_HYSTERESIS),
+		.scan_index = CHANNEL_SCAN_INDEX_Y,
+	}, {
+		.type = IIO_GRAVITY,
+		.modified = 1,
+		.channel2 = IIO_MOD_Z,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |
+		BIT(IIO_CHAN_INFO_SCALE) |
+		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+		BIT(IIO_CHAN_INFO_HYSTERESIS),
+		.scan_index = CHANNEL_SCAN_INDEX_Z,
+	}
+};
+
 /* Adjust channel real bits based on report descriptor */
 static void accel_3d_adjust_channel_bit_mask(struct iio_chan_spec *channels,
 						int channel, int size)
@@ -114,6 +149,8 @@ static int accel_3d_read_raw(struct iio_dev *indio_dev,
 	int report_id = -1;
 	u32 address;
 	int ret_type;
+	struct hid_sensor_hub_device *hsdev =
+					accel_state->common_attributes.hsdev;
 
 	*val = 0;
 	*val2 = 0;
@@ -125,8 +162,7 @@ static int accel_3d_read_raw(struct iio_dev *indio_dev,
 		if (report_id >= 0)
 			*val = sensor_hub_input_attr_get_raw_value(
 					accel_state->common_attributes.hsdev,
-					HID_USAGE_SENSOR_ACCEL_3D, address,
-					report_id,
+					hsdev->usage, address, report_id,
 					SENSOR_HUB_SYNC);
 		else {
 			*val = 0;
@@ -288,7 +324,7 @@ static int accel_3d_parse_report(struct platform_device *pdev,
 			st->accel[2].index, st->accel[2].report_id);
 
 	st->scale_precision = hid_sensor_format_scale(
-				HID_USAGE_SENSOR_ACCEL_3D,
+				hsdev->usage,
 				&st->accel[CHANNEL_SCAN_INDEX_X],
 				&st->scale_pre_decml, &st->scale_post_decml);
 
@@ -311,9 +347,12 @@ static int accel_3d_parse_report(struct platform_device *pdev,
 static int hid_accel_3d_probe(struct platform_device *pdev)
 {
 	int ret = 0;
-	static const char *name = "accel_3d";
+	static const char *name;
 	struct iio_dev *indio_dev;
 	struct accel_3d_state *accel_state;
+	const struct iio_chan_spec *channel_spec;
+	int channel_size;
+
 	struct hid_sensor_hub_device *hsdev = pdev->dev.platform_data;
 
 	indio_dev = devm_iio_device_alloc(&pdev->dev,
@@ -327,24 +366,30 @@ static int hid_accel_3d_probe(struct platform_device *pdev)
 	accel_state->common_attributes.hsdev = hsdev;
 	accel_state->common_attributes.pdev = pdev;
 
-	ret = hid_sensor_parse_common_attributes(hsdev,
-					HID_USAGE_SENSOR_ACCEL_3D,
+	if (hsdev->usage == HID_USAGE_SENSOR_ACCEL_3D) {
+		name = "accel_3d";
+		channel_spec = accel_3d_channels;
+		channel_size = sizeof(accel_3d_channels);
+	} else {
+		name = "gravity";
+		channel_spec = gravity_channels;
+		channel_size = sizeof(gravity_channels);
+	}
+	ret = hid_sensor_parse_common_attributes(hsdev, hsdev->usage,
 					&accel_state->common_attributes);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to setup common attributes\n");
 		return ret;
 	}
+	indio_dev->channels = kmemdup(channel_spec, channel_size, GFP_KERNEL);
 
-	indio_dev->channels = kmemdup(accel_3d_channels,
-				      sizeof(accel_3d_channels), GFP_KERNEL);
 	if (!indio_dev->channels) {
 		dev_err(&pdev->dev, "failed to duplicate channels\n");
 		return -ENOMEM;
 	}
-
 	ret = accel_3d_parse_report(pdev, hsdev,
 				(struct iio_chan_spec *)indio_dev->channels,
-				    HID_USAGE_SENSOR_ACCEL_3D, accel_state);
+				hsdev->usage, accel_state);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to setup attributes\n");
 		goto error_free_dev_mem;
@@ -379,7 +424,7 @@ static int hid_accel_3d_probe(struct platform_device *pdev)
 	accel_state->callbacks.send_event = accel_3d_proc_event;
 	accel_state->callbacks.capture_sample = accel_3d_capture_sample;
 	accel_state->callbacks.pdev = pdev;
-	ret = sensor_hub_register_callback(hsdev, HID_USAGE_SENSOR_ACCEL_3D,
+	ret = sensor_hub_register_callback(hsdev, hsdev->usage,
 					&accel_state->callbacks);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "callback reg failed\n");
@@ -406,7 +451,7 @@ static int hid_accel_3d_remove(struct platform_device *pdev)
 	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
 	struct accel_3d_state *accel_state = iio_priv(indio_dev);
 
-	sensor_hub_remove_callback(hsdev, HID_USAGE_SENSOR_ACCEL_3D);
+	sensor_hub_remove_callback(hsdev, hsdev->usage);
 	iio_device_unregister(indio_dev);
 	hid_sensor_remove_trigger(&accel_state->common_attributes);
 	iio_triggered_buffer_cleanup(indio_dev);
@@ -420,6 +465,9 @@ static const struct platform_device_id hid_accel_3d_ids[] = {
 		/* Format: HID-SENSOR-usage_id_in_hex_lowercase */
 		.name = "HID-SENSOR-200073",
 	},
+	{	/* gravity sensor */
+		.name = "HID-SENSOR-20007b",
+	},
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(platform, hid_accel_3d_ids);

include/linux/hid-sensor-ids.h

@@ -52,6 +52,9 @@
 #define HID_USAGE_SENSOR_ANGL_VELOCITY_Y_AXIS			0x200458
 #define HID_USAGE_SENSOR_ANGL_VELOCITY_Z_AXIS			0x200459
 
+/* Gravity vector */
+#define HID_USAGE_SENSOR_GRAVITY_VECTOR				0x20007B
+
 /* ORIENTATION: Compass 3D: (200083) */
 #define HID_USAGE_SENSOR_COMPASS_3D				0x200083
 #define HID_USAGE_SENSOR_DATA_ORIENTATION			0x200470