Re: [PATCH 2/8] iio: hid-sensor-als: Add light color temperature support

[Basavaraj Natikar <bnatikar@amd.com>]

On 9/17/2023 4:30 PM, Jonathan Cameron wrote:
> On Fri, 15 Sep 2023 10:46:57 +0530
> Basavaraj Natikar <Basavaraj.Natikar@amd.com> wrote:
>
>> In most cases, ambient color sensors also support light color temperature.
>> As a result, add support of light color temperature.
>>
>> Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
>> ---
>>  drivers/iio/light/hid-sensor-als.c | 33 ++++++++++++++++++++++++++++++
>>  include/linux/hid-sensor-ids.h     |  1 +
>>  2 files changed, 34 insertions(+)
>>
>> diff --git a/drivers/iio/light/hid-sensor-als.c b/drivers/iio/light/hid-sensor-als.c
>> index 48879e233aec..220fb93fea6d 100644
>> --- a/drivers/iio/light/hid-sensor-als.c
>> +++ b/drivers/iio/light/hid-sensor-als.c
>> @@ -16,6 +16,7 @@
>>  enum {
>>  	CHANNEL_SCAN_INDEX_INTENSITY = 0,
>>  	CHANNEL_SCAN_INDEX_ILLUM = 1,
> Either drop, the = 1 or keep consistency for TEMP. 
> I don't think the = 1 is useful so I'd drop it.
>
>> +	CHANNEL_SCAN_INDEX_COLOR_TEMP,
>>  	CHANNEL_SCAN_INDEX_MAX
>>  };
>>  
>> @@ -65,6 +66,18 @@ static const struct iio_chan_spec als_channels[] = {
>>  		BIT(IIO_CHAN_INFO_HYSTERESIS_RELATIVE),
>>  		.scan_index = CHANNEL_SCAN_INDEX_ILLUM,
>>  	},
>> +	{
>> +		.type = IIO_TEMP,
> Using a temperature channel for color temp is a bit of a stretch,
> Particularly as it's likely we will see light sensors with actual
> air temperature sensors in them at somepoint even if we don't have
> any already.
>
> So this needs a new channel type
> IIO_COLORTEMP or similar.
>
> Units for this probably want to be kelvin unlike the mili decrees centigrade
> used for IIO_TEMP.
>
>> +		.modified = 1,
>> +		.channel2 = IIO_MOD_TEMP_AMBIENT,
> I don't really see the modifier as useful here. That exists for thermocouple
> type systems where it is necessary to know ambient vs sample temperatures.

Sure Jonathan, I will address all comments in this series in v2.
Also, can i add new channel type IIO_COLORTEMP with following channel index
for light color temperature ?
       {
                .type = IIO_COLORTEMP,
                .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) |
                        BIT(IIO_CHAN_INFO_HYSTERESIS_RELATIVE),
                .scan_index = CHANNEL_SCAN_INDEX_COLOR_TEMP,
        }

Thanks,
--
Basavaraj

>
>
>> +		.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) |
>> +			BIT(IIO_CHAN_INFO_HYSTERESIS_RELATIVE),
>> +		.scan_index = CHANNEL_SCAN_INDEX_COLOR_TEMP,
>> +	},
>>  	IIO_CHAN_SOFT_TIMESTAMP(CHANNEL_SCAN_INDEX_TIMESTAMP)
>>  };
>>  
>> @@ -103,6 +116,11 @@ static int als_read_raw(struct iio_dev *indio_dev,
>>  			min = als_state->als_illum[chan->scan_index].logical_minimum;
>>  			address = HID_USAGE_SENSOR_LIGHT_ILLUM;
>>  			break;
>> +		case  CHANNEL_SCAN_INDEX_COLOR_TEMP:
>> +			report_id = als_state->als_illum[chan->scan_index].report_id;
>> +			min = als_state->als_illum[chan->scan_index].logical_minimum;
>> +			address = HID_USAGE_SENSOR_LIGHT_COLOR_TEMPERATURE;
>> +			break;
>>  		default:
>>  			report_id = -1;
>>  			break;
>> @@ -223,6 +241,10 @@ static int als_capture_sample(struct hid_sensor_hub_device *hsdev,
>>  		als_state->scan.illum[CHANNEL_SCAN_INDEX_ILLUM] = sample_data;
>>  		ret = 0;
>>  		break;
>> +	case HID_USAGE_SENSOR_LIGHT_COLOR_TEMPERATURE:
>> +		als_state->scan.illum[CHANNEL_SCAN_INDEX_COLOR_TEMP] = sample_data;
>> +		ret = 0;
>> +		break;
>>  	case HID_USAGE_SENSOR_TIME_TIMESTAMP:
>>  		als_state->timestamp = hid_sensor_convert_timestamp(&als_state->common_attributes,
>>  								    *(s64 *)raw_data);
>> @@ -256,6 +278,17 @@ static int als_parse_report(struct platform_device *pdev,
>>  			st->als_illum[i].report_id);
>>  	}
>>  
>> +	ret = sensor_hub_input_get_attribute_info(hsdev, HID_INPUT_REPORT, usage_id,
>> +						  HID_USAGE_SENSOR_LIGHT_COLOR_TEMPERATURE,
>> +						  &st->als_illum[CHANNEL_SCAN_INDEX_COLOR_TEMP]);
>> +	if (ret < 0)
>> +		return ret;
>> +	als_adjust_channel_bit_mask(channels, CHANNEL_SCAN_INDEX_COLOR_TEMP,
>> +				    st->als_illum[CHANNEL_SCAN_INDEX_COLOR_TEMP].size);
>> +
>> +	dev_dbg(&pdev->dev, "als %x:%x\n", st->als_illum[CHANNEL_SCAN_INDEX_COLOR_TEMP].index,
>> +		st->als_illum[CHANNEL_SCAN_INDEX_COLOR_TEMP].report_id);
>> +
>>  	st->scale_precision = hid_sensor_format_scale(usage_id,
>>  						      &st->als_illum[CHANNEL_SCAN_INDEX_INTENSITY],
>>  						      &st->scale_pre_decml, &st->scale_post_decml);
>> diff --git a/include/linux/hid-sensor-ids.h b/include/linux/hid-sensor-ids.h
>> index 13b1e65fbdcc..8af4fb3e0254 100644
>> --- a/include/linux/hid-sensor-ids.h
>> +++ b/include/linux/hid-sensor-ids.h
>> @@ -21,6 +21,7 @@
>>  #define HID_USAGE_SENSOR_ALS					0x200041
>>  #define HID_USAGE_SENSOR_DATA_LIGHT				0x2004d0
>>  #define HID_USAGE_SENSOR_LIGHT_ILLUM				0x2004d1
>> +#define HID_USAGE_SENSOR_LIGHT_COLOR_TEMPERATURE		0x2004d2
>>  
>>  /* PROX (200011) */
>>  #define HID_USAGE_SENSOR_PROX                                   0x200011