[PATCH v4 3/4] iio: hid-sensor-magn-3d: Scan for usage attributes before setting up iio channels

[Reyad Attiyat <reyad.attiyat@gmail.com>]

Scan for and count the HID usage attributes supported by the driver.
This allows for the driver to only setup the IIO channels for the
sensor usages present in the HID USB reports.

Signed-off-by: Reyad Attiyat <reyad.attiyat@gmail.com>
---
 drivers/iio/magnetometer/hid-sensor-magn-3d.c | 111 +++++++++++++++++---------
 1 file changed, 75 insertions(+), 36 deletions(-)

diff --git a/drivers/iio/magnetometer/hid-sensor-magn-3d.c b/drivers/iio/magnetometer/hid-sensor-magn-3d.c
index 41cf29e..070d20e 100644
--- a/drivers/iio/magnetometer/hid-sensor-magn-3d.c
+++ b/drivers/iio/magnetometer/hid-sensor-magn-3d.c
@@ -42,7 +42,8 @@ struct magn_3d_state {
 	struct hid_sensor_hub_callbacks callbacks;
 	struct hid_sensor_common common_attributes;
 	struct hid_sensor_hub_attribute_info magn[MAGN_3D_CHANNEL_MAX];
-	u32 magn_val[MAGN_3D_CHANNEL_MAX];
+	u32 *magn_val_addr[MAGN_3D_CHANNEL_MAX];
+	u32 *iio_val;
 	int scale_pre_decml;
 	int scale_post_decml;
 	int scale_precision;
@@ -221,8 +222,8 @@ static int magn_3d_proc_event(struct hid_sensor_hub_device *hsdev,
 	dev_dbg(&indio_dev->dev, "magn_3d_proc_event\n");
 	if (atomic_read(&magn_state->common_attributes.data_ready))
 		hid_sensor_push_data(indio_dev,
-				magn_state->magn_val,
-				sizeof(magn_state->magn_val));
+				magn_state->iio_val,
+				sizeof(magn_state->iio_val));
 
 	return 0;
 }
@@ -236,52 +237,99 @@ static int magn_3d_capture_sample(struct hid_sensor_hub_device *hsdev,
 	struct iio_dev *indio_dev = platform_get_drvdata(priv);
 	struct magn_3d_state *magn_state = iio_priv(indio_dev);
 	int offset;
-	int ret = -EINVAL;
+	int ret = 0;
+	u32 *iio_val = NULL;
 
 	switch (usage_id) {
 	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS:
 	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Y_AXIS:
 	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Z_AXIS:
 		offset = usage_id - HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS;
-		magn_state->magn_val[CHANNEL_SCAN_INDEX_X + offset] =
-						*(u32 *)raw_data;
-		ret = 0;
+		iio_val = magn_state->magn_val_addr[CHANNEL_SCAN_INDEX_X + offset];
+
 	break;
 	default:
-		break;
+		return -EINVAL;
 	}
 
+	if(iio_val)
+		*iio_val = *(u32 *)raw_data;
+	else
+		ret = -EINVAL;
+
 	return ret;
 }
 
 /* Parse report which is specific to an usage id*/
 static int magn_3d_parse_report(struct platform_device *pdev,
 				struct hid_sensor_hub_device *hsdev,
-				struct iio_chan_spec *channels,
+				struct iio_chan_spec **channels,
+				int *chan_count,
 				unsigned usage_id,
 				struct magn_3d_state *st)
 {
-	int ret;
+	int ret = 0;
 	int i;
+	int attr_count = 0;
+
+	/* Scan for each usage attribute supported */
+	for (i = 0; i < MAGN_3D_CHANNEL_MAX; i++) {
+		u32 address = magn_3d_addresses[i];
 
-	for (i = 0; i <= CHANNEL_SCAN_INDEX_Z; ++i) {
+		/* Check if usage attribute exists in the sensor hub device */
 		ret = sensor_hub_input_get_attribute_info(hsdev,
-				HID_INPUT_REPORT,
-				usage_id,
-				HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS + i,
-				&st->magn[CHANNEL_SCAN_INDEX_X + i]);
-		if (ret < 0)
-			break;
-		magn_3d_adjust_channel_bit_mask(channels,
-				CHANNEL_SCAN_INDEX_X + i,
-				st->magn[CHANNEL_SCAN_INDEX_X + i].size);
+			HID_INPUT_REPORT,
+			usage_id,
+			address,
+			&(st->magn[i]));
+		if (!ret)
+			attr_count++;
 	}
-	dev_dbg(&pdev->dev, "magn_3d %x:%x, %x:%x, %x:%x\n",
+
+	dev_dbg(&pdev->dev, "magn_3d Found %d usage attributes\n",
+			attr_count);
+	dev_dbg(&pdev->dev, "magn_3d X: %x:%x Y: %x:%x Z: %x:%x\n",
 			st->magn[0].index,
 			st->magn[0].report_id,
 			st->magn[1].index, st->magn[1].report_id,
 			st->magn[2].index, st->magn[2].report_id);
 
+	if (attr_count > 0)
+		ret = 0;
+	else
+		return  -EINVAL;
+
+	/* Setup IIO channel array */
+	*channels = devm_kcalloc(&pdev->dev, attr_count,
+								sizeof(struct iio_chan_spec),
+								GFP_KERNEL);
+	if (!*channels) {
+		dev_err(&pdev->dev, "failed to allocate space for iio channels\n");
+		return -ENOMEM;
+	}
+
+	st->iio_val = devm_kcalloc(&pdev->dev, attr_count,
+								sizeof(u32),
+								GFP_KERNEL);
+	if (!st->iio_val) {
+		dev_err(&pdev->dev, "failed to allocate space for iio values array\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0, *chan_count = 0;
+	    i < MAGN_3D_CHANNEL_MAX && *chan_count < attr_count;
+		i++)
+	{
+		if (st->magn[i].index >= 0) {
+			/* Setup IIO channel struct */
+			*channels[*chan_count] = magn_3d_channels[i];
+
+			st->magn_val_addr[i] = &(st->iio_val[*chan_count]);
+			magn_3d_adjust_channel_bit_mask(*channels, *chan_count, st->magn[i].size);
+			(*chan_count)++;
+		}
+	}
+
 	st->scale_precision = hid_sensor_format_scale(
 				HID_USAGE_SENSOR_COMPASS_3D,
 				&st->magn[CHANNEL_SCAN_INDEX_X],
@@ -311,6 +359,7 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
 	struct magn_3d_state *magn_state;
 	struct hid_sensor_hub_device *hsdev = pdev->dev.platform_data;
 	struct iio_chan_spec *channels;
+	int chan_count = 0;
 
 	indio_dev = devm_iio_device_alloc(&pdev->dev,
 					  sizeof(struct magn_3d_state));
@@ -331,22 +380,15 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	channels = kmemdup(magn_3d_channels, sizeof(magn_3d_channels),
-			   GFP_KERNEL);
-	if (!channels) {
-		dev_err(&pdev->dev, "failed to duplicate channels\n");
-		return -ENOMEM;
-	}
-
-	ret = magn_3d_parse_report(pdev, hsdev, channels,
-				HID_USAGE_SENSOR_COMPASS_3D, magn_state);
+	ret = magn_3d_parse_report(pdev, hsdev, &channels,
+				&chan_count, HID_USAGE_SENSOR_COMPASS_3D, magn_state);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to setup attributes\n");
-		goto error_free_dev_mem;
+		return ret;
 	}
 
 	indio_dev->channels = channels;
-	indio_dev->num_channels = ARRAY_SIZE(magn_3d_channels);
+	indio_dev->num_channels = chan_count;
 	indio_dev->dev.parent = &pdev->dev;
 	indio_dev->info = &magn_3d_info;
 	indio_dev->name = name;
@@ -356,7 +398,7 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
 		NULL, NULL);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to initialize trigger buffer\n");
-		goto error_free_dev_mem;
+		return ret;
 	}
 	atomic_set(&magn_state->common_attributes.data_ready, 0);
 	ret = hid_sensor_setup_trigger(indio_dev, name,
@@ -390,8 +432,6 @@ error_remove_trigger:
 	hid_sensor_remove_trigger(&magn_state->common_attributes);
 error_unreg_buffer_funcs:
 	iio_triggered_buffer_cleanup(indio_dev);
-error_free_dev_mem:
-	kfree(indio_dev->channels);
 	return ret;
 }
 
@@ -406,7 +446,6 @@ static int hid_magn_3d_remove(struct platform_device *pdev)
 	iio_device_unregister(indio_dev);
 	hid_sensor_remove_trigger(&magn_state->common_attributes);
 	iio_triggered_buffer_cleanup(indio_dev);
-	kfree(indio_dev->channels);
 
 	return 0;
 }
-- 
1.9.3