Date: Sun, 4 Feb 2024 05:06:21 -0800
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: jikos@...nel.org, lars@...afoo.de, Basavaraj.Natikar@....com,
 linux-input@...r.kernel.org, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] iio: hid-sensor-als: Assign channels dynamically

Hi Jonathan,

On 1/13/24 08:03, Jonathan Cameron wrote:
> On Tue,  9 Jan 2024 10:00:04 -0800
> Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> 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@...ux.intel.com>
>> ---
>> 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.
Submitted v4 leaving gaps.
>
>
> 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.

Correct. But hid-sensor-hub core ignores return value, so it doesn't 
cause any issue.

But I sent a separate patch to fix this.


>
>> 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?)
Add this.
> 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.

Please check v4, if it solve the above issues.

Thanks,

Srinivas



> 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;

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