Re: [PATCH v3 1/4] iio: hid-sensor-als: Assign channels dynamically

[Jonathan Cameron]

On Tue,  9 Jan 2024 10:00:04 -0800
Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:

> Instead of assuming that every channel defined statically by
> als_channels[] is present, assign dynamically based on presence of the
> respective usage id in the descriptor. This will allow to register ALS
> with limited channel support. Append the timestamp as the last channel.
> 
> When not all usage ids are present, the scan index is adjusted to
> exclude unsupported channels.
> 
> There is no intentional function changes done.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
> ---
> v3:
> Addressed comments from Jonthan:
> 	- Remove channel allocation and move to iio_priv()
> 	- Parse all usage IDs in a single loop and continue
> 	for failure. This way the temperature and chromaticity
> 	will not need any special processing to parse usage ids.
> 	- Don't leave empty channel indexes

There isn't really a problem if you did want to leave them.
There are a number of other devices that do leave gaps and userspace
code shouldn't mind that.  I don't mind them being more tightly packed
though so this is also fine.


I was just looking at the driver and noticed one other oddity.
In als_capture_sample, it always returns -EINVAL if the timestamp channel
is being queried.

> 
> v2:
> New change
> 
>  drivers/iio/light/hid-sensor-als.c | 56 +++++++++++++++++++++---------
>  1 file changed, 39 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/light/hid-sensor-als.c b/drivers/iio/light/hid-sensor-als.c
> index 5cd27f04b45e..72a7c01c97f8 100644
> --- a/drivers/iio/light/hid-sensor-als.c
> +++ b/drivers/iio/light/hid-sensor-als.c
> @@ -25,17 +25,26 @@ struct als_state {
>  	struct hid_sensor_hub_callbacks callbacks;
>  	struct hid_sensor_common common_attributes;
>  	struct hid_sensor_hub_attribute_info als[CHANNEL_SCAN_INDEX_MAX];
> +	struct iio_chan_spec channels[CHANNEL_SCAN_INDEX_MAX + 1];
>  	struct {
>  		u32 illum[CHANNEL_SCAN_INDEX_MAX];
> +		u32 scan_index[CHANNEL_SCAN_INDEX_MAX];
This looks unlikely to end up right with a varying number of channels.
I'm assuming the device always captures all available channels.
As such, if there are 2 channels the timestamp will end up at byte 8 onwards.
If there are 3 channels, byte 16 onwards etc.

Usually when we have a floating timestamp like this we just rely on expanding
the channel array to leave space and force the alignment of that to be suitable
for taking a timestamp.

I'm a bit confused not to see available_scan_mask being set though.
If userspace previously requested illumination only would the data
have ended up in the right location (offset 0?)

If you set available_scan_masks to specify all channels then the
IIO core will move things around for you. If it's not provided then
it is up to the driver to figure out where to put the data.

Otherwise the patch looks fine to me.

Jonathan



>  		u64 timestamp __aligned(8);
>  	} scan;
>  	int scale_pre_decml;
>  	int scale_post_decml;
>  	int scale_precision;
>  	int value_offset;
> +	int num_channels;
>  	s64 timestamp;
>  };
>  
> +/* The order of usage ids must match scan index starting from CHANNEL_SCAN_INDEX_INTENSITY */
> +static const u32 als_usage_ids[] = {
> +	HID_USAGE_SENSOR_LIGHT_ILLUM,
> +	HID_USAGE_SENSOR_LIGHT_ILLUM,
> +};
> +
>  static const u32 als_sensitivity_addresses[] = {
>  	HID_USAGE_SENSOR_DATA_LIGHT,
>  	HID_USAGE_SENSOR_LIGHT_ILLUM,
> @@ -216,11 +225,14 @@ static int als_capture_sample(struct hid_sensor_hub_device *hsdev,
>  	struct als_state *als_state = iio_priv(indio_dev);
>  	int ret = -EINVAL;
>  	u32 sample_data = *(u32 *)raw_data;
> +	int scan_index;
>  
>  	switch (usage_id) {
>  	case HID_USAGE_SENSOR_LIGHT_ILLUM:
> -		als_state->scan.illum[CHANNEL_SCAN_INDEX_INTENSITY] = sample_data;
> -		als_state->scan.illum[CHANNEL_SCAN_INDEX_ILLUM] = sample_data;
> +		scan_index = als_state->scan.scan_index[CHANNEL_SCAN_INDEX_INTENSITY];
> +		als_state->scan.illum[scan_index] = sample_data;
> +		scan_index = als_state->scan.scan_index[CHANNEL_SCAN_INDEX_ILLUM];
> +		als_state->scan.illum[scan_index] = sample_data;
>  		ret = 0;
>  		break;
>  	case HID_USAGE_SENSOR_TIME_TIMESTAMP:
> @@ -237,27 +249,39 @@ static int als_capture_sample(struct hid_sensor_hub_device *hsdev,
>  /* Parse report which is specific to an usage id*/
>  static int als_parse_report(struct platform_device *pdev,
>  				struct hid_sensor_hub_device *hsdev,
> -				struct iio_chan_spec *channels,
>  				unsigned usage_id,
>  				struct als_state *st)
>  {
> -	int ret;
> +	struct iio_chan_spec *channels;
> +	int ret, index = 0;
>  	int i;
>  
> +	channels = st->channels;
> +
>  	for (i = 0; i <= CHANNEL_SCAN_INDEX_ILLUM; ++i) {
>  		ret = sensor_hub_input_get_attribute_info(hsdev,
>  						HID_INPUT_REPORT,
>  						usage_id,
> -						HID_USAGE_SENSOR_LIGHT_ILLUM,
> +						als_usage_ids[i],
>  						&st->als[i]);
>  		if (ret < 0)
> -			return ret;
> -		als_adjust_channel_bit_mask(channels, i, st->als[i].size);
> +			continue;
> +
> +		channels[index] = als_channels[i];
> +		st->scan.scan_index[i] = index;
> +
> +		als_adjust_channel_bit_mask(channels, index, st->als[i].size);
> +		++index;
>  
>  		dev_dbg(&pdev->dev, "als %x:%x\n", st->als[i].index,
>  			st->als[i].report_id);
>  	}
>  
> +	st->num_channels = index;
> +	/* Return success even if one usage id is present */
> +	if (index)
> +		ret = 0;
> +
>  	st->scale_precision = hid_sensor_format_scale(usage_id,
>  				&st->als[CHANNEL_SCAN_INDEX_INTENSITY],
>  				&st->scale_pre_decml, &st->scale_post_decml);
> @@ -293,15 +317,7 @@ static int hid_als_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	indio_dev->channels = devm_kmemdup(&pdev->dev, als_channels,
> -					   sizeof(als_channels), GFP_KERNEL);
> -	if (!indio_dev->channels) {
> -		dev_err(&pdev->dev, "failed to duplicate channels\n");
> -		return -ENOMEM;
> -	}
> -
>  	ret = als_parse_report(pdev, hsdev,
> -			       (struct iio_chan_spec *)indio_dev->channels,
>  			       hsdev->usage,
>  			       als_state);
>  	if (ret) {
> @@ -309,8 +325,14 @@ static int hid_als_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	indio_dev->num_channels =
> -				ARRAY_SIZE(als_channels);
> +	/* Add timestamp channel */
> +	als_state->channels[als_state->num_channels] = als_channels[CHANNEL_SCAN_INDEX_TIMESTAMP];
> +	als_state->channels[als_state->num_channels].scan_index = als_state->num_channels;
> +
> +	/* +1 for adding timestamp channel */
> +	indio_dev->num_channels = als_state->num_channels + 1;
> +
> +	indio_dev->channels = als_state->channels;
>  	indio_dev->info = &als_info;
>  	indio_dev->name = name;
>  	indio_dev->modes = INDIO_DIRECT_MODE;