Date:	Sat, 21 Jun 2014 12:19:56 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Reyad Attiyat <reyad.attiyat@...il.com>,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	srinivas.pandruvada@...ux.intel.com
Subject: Re: [PATCH v3 3/3] iio: hid-sensor-magn-3d: Add support for rotation
 from north usage attributes

On 16/06/14 23:30, Reyad Attiyat wrote:
> Added the ability for this driver to scan for a range of hid usage attributes.
> This allows for dynamic creation of iio channels such as rotation from north
> and/or magnetic flux axises (X, Y, Z).
>
> Signed-off-by: Reyad Attiyat <reyad.attiyat@...il.com>
Hi Reyad,

I'm afraid I hadn't taken as close a look at this as I should for previous
versions.  There are some nasty bugs introduced by your refactoring.
The fundamental approach is fine, but you've moved more things than
make sense in some cases.

With hind sight perhaps it would have been possible to break this patch
up into a series of small easily reviewed steps.

Anyhow, take a hard look at the error paths in the code as someone of them
are thorougly broken.  The channel setup function does an awful lot more
than setup the channels and it should not do so.  Moving other stuff in
there makes the code harder to follow and is responsible for at least
a few bugs that otherwise would not have occured.

Thanks,

Jonathan
> ---
>   drivers/iio/magnetometer/hid-sensor-magn-3d.c | 394 +++++++++++++++++---------
>   1 file changed, 266 insertions(+), 128 deletions(-)
>
> diff --git a/drivers/iio/magnetometer/hid-sensor-magn-3d.c b/drivers/iio/magnetometer/hid-sensor-magn-3d.c
> index 41cf29e..73e1272 100644
> --- a/drivers/iio/magnetometer/hid-sensor-magn-3d.c
> +++ b/drivers/iio/magnetometer/hid-sensor-magn-3d.c
> @@ -35,6 +35,10 @@ enum magn_3d_channel {
>   	CHANNEL_SCAN_INDEX_X,
>   	CHANNEL_SCAN_INDEX_Y,
>   	CHANNEL_SCAN_INDEX_Z,
> +	CHANNEL_SCAN_INDEX_NORTH_MAGN,
> +	CHANNEL_SCAN_INDEX_NORTH_TRUE,
> +	CHANNEL_SCAN_INDEX_NORTH_MAGN_TILT_COMP,
> +	CHANNEL_SCAN_INDEX_NORTH_TRUE_TILT_COMP,
>   	MAGN_3D_CHANNEL_MAX,
>   };
>
> @@ -42,63 +46,47 @@ 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;
>   	int value_offset;
>   };
>
> -static const u32 magn_3d_addresses[MAGN_3D_CHANNEL_MAX] = {
> -	HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS,
> -	HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Y_AXIS,
> -	HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Z_AXIS
> -};
>
> -/* Channel definitions */
> -static const struct iio_chan_spec magn_3d_channels[] = {
> -	{
> -		.type = IIO_MAGN,
> -		.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_MAGN,
> -		.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_MAGN,
> -		.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,
> +/* Find index into magn_3d_state magn[] and magn_val_addr[] from HID Usage  */
> +static int magn_3d_usage_id_to_chan_index(unsigned usage_id){
> +	int offset;
> +
> +	switch (usage_id) {
> +	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS:
> +		offset = CHANNEL_SCAN_INDEX_X;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Y_AXIS:
> +		offset = CHANNEL_SCAN_INDEX_Y;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Z_AXIS:
> +		offset = CHANNEL_SCAN_INDEX_Z;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_COMP_MAGN_NORTH:
> +		offset = CHANNEL_SCAN_INDEX_NORTH_MAGN_TILT_COMP;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_COMP_TRUE_NORTH:
> +		offset = CHANNEL_SCAN_INDEX_NORTH_TRUE_TILT_COMP;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_MAGN_NORTH:
> +		offset = CHANNEL_SCAN_INDEX_NORTH_MAGN;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_TRUE_NORTH:
> +		offset = CHANNEL_SCAN_INDEX_NORTH_TRUE;
> +		break;
> +	default:
> +		offset = -EINVAL;
> +		break;
>   	}
> -};
>
> -/* Adjust channel real bits based on report descriptor */
> -static void magn_3d_adjust_channel_bit_mask(struct iio_chan_spec *channels,
> -						int channel, int size)
> -{
> -	channels[channel].scan_type.sign = 's';
> -	/* Real storage bits will change based on the report desc. */
> -	channels[channel].scan_type.realbits = size * 8;
> -	/* Maximum size of a sample to capture is u32 */
> -	channels[channel].scan_type.storagebits = sizeof(u32) * 8;
> +	return offset;
>   }
>
>   /* Channel read_raw handler */
> @@ -109,11 +97,14 @@ static int magn_3d_read_raw(struct iio_dev *indio_dev,
>   {
>   	struct magn_3d_state *magn_state = iio_priv(indio_dev);
>   	int report_id = -1;
> -	u32 address;
> +	unsigned usage_id;
> +	int chan_index = -1;
>   	int ret;
>   	int ret_type;
>   	s32 poll_value;
>
> +	dev_dbg(&indio_dev->dev, "magn_3d_read_raw\n");
> +
>   	*val = 0;
>   	*val2 = 0;
>   	switch (mask) {
> @@ -126,13 +117,17 @@ static int magn_3d_read_raw(struct iio_dev *indio_dev,
>   		hid_sensor_power_state(&magn_state->common_attributes, true);
>   		msleep_interruptible(poll_value * 2);
>
> +		usage_id = chan->address;
> +		chan_index = magn_3d_usage_id_to_chan_index(usage_id);
> +		if (chan_index < 0)
> +			return -EINVAL;
> +
>   		report_id =
> -			magn_state->magn[chan->scan_index].report_id;
> -		address = magn_3d_addresses[chan->scan_index];
> +			magn_state->magn[chan_index].report_id;
>   		if (report_id >= 0)
>   			*val = sensor_hub_input_attr_get_raw_value(
>   				magn_state->common_attributes.hsdev,
> -				HID_USAGE_SENSOR_COMPASS_3D, address,
> +				HID_USAGE_SENSOR_COMPASS_3D, usage_id,
>   				report_id);
>   		else {
>   			*val = 0;
> @@ -221,12 +216,13 @@ 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;
>   }
>
> +
>   /* Capture samples in local storage */
>   static int magn_3d_capture_sample(struct hid_sensor_hub_device *hsdev,
>   				unsigned usage_id,
> @@ -236,51 +232,138 @@ 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;
> +	u32 *magn_val;
> +	int ret = 0;
>
> -	switch (usage_id) {
> +	offset = magn_3d_usage_id_to_chan_index(usage_id);
> +	if (offset < 0)
> +		return -EINVAL;
> +
> +	magn_val = magn_state->magn_val_addr[offset];
> +	if (!magn_val)
> +		return -EINVAL;
> +
> +	*(magn_val) =  *(u32 *)raw_data;
> +
> +	return ret;
> +}
> +
> +/* Setup the iio_chan_spec for HID Usage ID */
> +static int magn_3d_setup_iio_chan(unsigned attr_usage_id,
> +				s32 size,
> +				struct iio_chan_spec *channel)
> +{
> +
> +	channel->modified = 1;
> +	channel->address = attr_usage_id;
> +
> +	switch (attr_usage_id){
> +	case HID_USAGE_SENSOR_ORIENT_COMP_MAGN_NORTH:
> +		channel->type = IIO_ROT;
> +		channel->channel2 = IIO_MOD_NORTH_MAGN_TILT_COMP;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_COMP_TRUE_NORTH:
> +		channel->type = IIO_ROT;
> +		channel->channel2 = IIO_MOD_NORTH_TRUE_TILT_COMP;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_MAGN_NORTH:
> +		channel->type = IIO_ROT;
> +		channel->channel2 = IIO_MOD_NORTH_MAGN;
> +		break;
> +	case HID_USAGE_SENSOR_ORIENT_TRUE_NORTH:
> +		channel->type = IIO_ROT;
> +		channel->channel2 = IIO_MOD_NORTH_TRUE;
> +		break;
>   	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS:
> +		channel->type = IIO_MAGN;
> +		channel->channel2 = IIO_MOD_X;
> +		break;
>   	case HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Y_AXIS:
> +		channel->type = IIO_MAGN;
> +		channel->channel2 = IIO_MOD_Y;
> +		break;
>   	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;
> -	break;
> -	default:
> +		channel->type = IIO_MAGN;
> +		channel->channel2 = IIO_MOD_Z;
>   		break;
> +	default:
> +		return -EINVAL;
>   	}
>
> -	return ret;
> +	channel->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
> +	channel->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);
> +
> +	channel->scan_type.sign = 's';
> +	/* Real storage bits will change based on the report desc. */
> +	channel->scan_type.realbits = size  * 8;
> +	/* Maximum size of a sample to capture is u32 */
> +	channel->scan_type.storagebits = sizeof(u32) * 8;
> +
> +
One blank line only here please.
> +	return 0;
>   }
>
> -/* 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,
Please fix the multiline comment syntax.  Even better, use kernel-doc
formatting.
> +/* Scan a HID report for a range of attribute usages.
> + * Returns the count of attribute usages found.
> + */
> +static int magn_3d_scan_range_usage_ids(struct hid_sensor_hub_device *hsdev,
>   				unsigned usage_id,
> +				unsigned start_id,
> +				unsigned end_id,
>   				struct magn_3d_state *st)
>   {
> +	int count = 0;
>   	int ret;
> -	int i;
> +	int id;
>
> -	for (i = 0; i <= CHANNEL_SCAN_INDEX_Z; ++i) {
> +	for (id = start_id; id <= end_id; id++) {
> +		int i;
> +
> +		i = magn_3d_usage_id_to_chan_index(id);
> +		if(i < 0)
> +			continue;
> +
> +		/* 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);
> +				id,
> +				&(st->magn[i]));
> +		if (ret == 0)
> +			count++;
> +	}
> +
> +	return count;
> +}
> +
> +/* Parse the HID report and return number of reports found */
> +static int magn_3d_parse_report(struct platform_device *pdev,
> +				struct hid_sensor_hub_device *hsdev,
> +				unsigned usage_id,
> +				int* attribute_count,
> +				struct magn_3d_state *st)
> +{
> +	int usage_count = 0;
> +
> +	usage_count += magn_3d_scan_range_usage_ids(hsdev, usage_id,
> +					HID_USAGE_SENSOR_ORIENT_COMP_MAGN_NORTH,
> +					HID_USAGE_SENSOR_ORIENT_TRUE_NORTH,
> +					st);
> +
> +	usage_count += magn_3d_scan_range_usage_ids(hsdev, usage_id,
> +					HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_X_AXIS,
> +					HID_USAGE_SENSOR_ORIENT_MAGN_FLUX_Z_AXIS,
> +					st);
> +
> +	if (attribute_count != NULL && usage_count > 0) {
> +		*attribute_count = usage_count;
> +	} else {
> +		return -EINVAL;
>   	}
> -	dev_dbg(&pdev->dev, "magn_3d %x:%x, %x:%x, %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);
>
>   	st->scale_precision = hid_sensor_format_scale(
>   				HID_USAGE_SENSOR_COMPASS_3D,
> @@ -299,54 +382,60 @@ static int magn_3d_parse_report(struct platform_device *pdev,
>   			st->common_attributes.sensitivity.report_id);
>   	}
>
> -	return ret;
> +	dev_dbg(&pdev->dev, "magn_3d_parse_reports found %d attribute usages\n", usage_count);
> +
> +	return 0;
>   }
>
> -/* Function to initialize the processing for usage id */
> -static int hid_magn_3d_probe(struct platform_device *pdev)
> +/* Setup iio channels */

Keep this function much more foccused on just setting up the channels.
Right now it's introduced a whole load of bugs into your remove because you
aren't unwinding what this does in the error paths.
So this function should fill the channels array and return how many
there are.  Nothing else.  All the other setups stuff that was previously
in the probe function should go back there and be correctly unwound on
any errors (as it previously was).

This is one of those annoying cases where diff is making it hard to
see what the reorganization was. Oh well.

> +static int magn_3d_setup_iio_channels(struct platform_device *pdev,
> +				struct iio_dev *indio_dev,
> +				unsigned usage_id,
> +				int attr_count,
> +				struct magn_3d_state *st)
>   {
> -	int ret = 0;
> +	int ret;
>   	static char *name = "magn_3d";
> -	struct iio_dev *indio_dev;
> -	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;
> +	int i;
>
> -	indio_dev = devm_iio_device_alloc(&pdev->dev,
> -					  sizeof(struct magn_3d_state));
> -	if (indio_dev == NULL)
> +	/* Allocate IIO channels struct */
> +	channels = devm_kcalloc(&pdev->dev,
> +			attr_count,
> +			sizeof(struct iio_chan_spec),
> +			GFP_KERNEL);
> +	if (!channels) {
> +		dev_err(&pdev->dev, "failed to allocate memory for iio channels\n");
>   		return -ENOMEM;
> -
> -	platform_set_drvdata(pdev, indio_dev);
> -
> -	magn_state = iio_priv(indio_dev);
> -	magn_state->common_attributes.hsdev = hsdev;
> -	magn_state->common_attributes.pdev = pdev;
> -
> -	ret = hid_sensor_parse_common_attributes(hsdev,
> -				HID_USAGE_SENSOR_COMPASS_3D,
> -				&magn_state->common_attributes);
> -	if (ret) {
> -		dev_err(&pdev->dev, "failed to setup common attributes\n");
> -		return ret;
>   	}
>
> -	channels = kmemdup(magn_3d_channels, sizeof(magn_3d_channels),
> -			   GFP_KERNEL);
> -	if (!channels) {
> -		dev_err(&pdev->dev, "failed to duplicate channels\n");
> +	/* Allocate IIO values array */
> +	st->iio_val = devm_kcalloc(&pdev->dev,
> +				attr_count,
> +				sizeof(u32),
> +				GFP_KERNEL);
> +	if (!(st->iio_val)) {
> +		dev_err(&pdev->dev, "failed to allocate memory for iio value\n");
>   		return -ENOMEM;
>   	}
>
> -	ret = magn_3d_parse_report(pdev, hsdev, channels,
> -				HID_USAGE_SENSOR_COMPASS_3D, magn_state);
> -	if (ret) {
> -		dev_err(&pdev->dev, "failed to setup attributes\n");
> -		goto error_free_dev_mem;
> +	/* Setup each IIO channel that is present */
> +	for (i = 0; i < MAGN_3D_CHANNEL_MAX && chan_count < attr_count; i++){
> +		u32 attr = st->magn[i].attrib_id;
> +		s32 size = st->magn[i].size;
> +
> +		if (attr != 0 && size > 0) {
> +			ret = magn_3d_setup_iio_chan(attr, size, &(channels[chan_count]));
> +			if (ret == 0) {
> +				chan_count++;
> +				st->magn_val_addr[i] = &(st->iio_val[chan_count]);
> +			}
> +		}
>   	}
>
>   	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;
> @@ -358,9 +447,9 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
>   		dev_err(&pdev->dev, "failed to initialize trigger buffer\n");
>   		goto error_free_dev_mem;
>   	}
> -	atomic_set(&magn_state->common_attributes.data_ready, 0);
> +	atomic_set(&st->common_attributes.data_ready, 0);
>   	ret = hid_sensor_setup_trigger(indio_dev, name,
> -					&magn_state->common_attributes);
> +					&st->common_attributes);
>   	if (ret < 0) {
>   		dev_err(&pdev->dev, "trigger setup failed\n");
>   		goto error_unreg_buffer_funcs;
> @@ -372,6 +461,65 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
>   		goto error_remove_trigger;
>   	}
>
> +	return 0;
> +
> +error_remove_trigger:
> +	hid_sensor_remove_trigger(&st->common_attributes);
> +error_unreg_buffer_funcs:
> +	iio_triggered_buffer_cleanup(indio_dev);
> +error_free_dev_mem:

These (as in the remove below) are unneeded.  Please take a look at the
devm docs if you don't understand why.
> +	devm_kfree(&pdev->dev, (void*) indio_dev->channels);
> +	devm_kfree(&pdev->dev, (void*) st->iio_val);
> +
> +	return -EINVAL;
> +}
> +
> +/* Function to initialize the processing for usage id */
> +static int hid_magn_3d_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct iio_dev *indio_dev;
> +	struct magn_3d_state *magn_state;
> +	struct hid_sensor_hub_device *hsdev = pdev->dev.platform_data;
> +	int report_attr_count = 0;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev,
> +					  sizeof(struct magn_3d_state));
> +	if (indio_dev == NULL)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	magn_state = iio_priv(indio_dev);
> +	magn_state->common_attributes.hsdev = hsdev;
> +	magn_state->common_attributes.pdev = pdev;
> +
> +	ret = hid_sensor_parse_common_attributes(hsdev,
> +				HID_USAGE_SENSOR_COMPASS_3D,
> +				&magn_state->common_attributes);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to setup common attributes\n");
> +		return ret;
> +	}
> +
> +	ret = magn_3d_parse_report(pdev, hsdev,
> +				HID_USAGE_SENSOR_COMPASS_3D,
> +				&report_attr_count,
> +				magn_state);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to setup attributes\n");
> +		return ret;
> +	}
> +
> +	ret = magn_3d_setup_iio_channels(pdev, indio_dev,
> +				HID_USAGE_SENSOR_COMPASS_3D,
> +				report_attr_count,
> +				magn_state);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to setup iio channel\n");
> +		return ret;
> +	}
> +
>   	magn_state->callbacks.send_event = magn_3d_proc_event;
>   	magn_state->callbacks.capture_sample = magn_3d_capture_sample;
>   	magn_state->callbacks.pdev = pdev;
> @@ -379,20 +527,9 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
>   					&magn_state->callbacks);
>   	if (ret < 0) {
>   		dev_err(&pdev->dev, "callback reg failed\n");
You need to unwind everything in the channel setup code here.  Nothing
unregisters the device for starters.

> -		goto error_iio_unreg;
>   	}
>
>   	return ret;
> -
> -error_iio_unreg:
> -	iio_device_unregister(indio_dev);
> -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;
>   }
>
>   /* Function to deinitialize the processing for usage id */
> @@ -406,7 +543,8 @@ 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);
> +	devm_kfree(&pdev->dev, (void*) magn_state->iio_val);
> +	devm_kfree(&pdev->dev, (void*) indio_dev->channels);
You don't need these here.  The whole point about devm resource
management is that they will get released on remove on the device
without it needing to be explicitly done.
>
>   	return 0;
>   }
>

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