linux-kernel - Re: [PATCH 2/2] iio: bu27034: Add a read only HWARDWAREGAIN

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Date: Mon, 17 Jun 2024 08:34:20 +0300
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Lars-Peter Clausen <lars@...afoo.de>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: bu27034: Add a read only HWARDWAREGAIN

On 6/15/24 20:50, Jonathan Cameron wrote:
> On Mon, 10 Jun 2024 13:01:40 +0300
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
> 
>> The ROHM BU27034 light sensor has two data channels for measuring
>> different frequencies of light. The result from these channels is
>> combined into Lux value while the raw channel values are reported via
>> intensity channels.
>>
>> Both of the intensity channels have adjustable gain setting which
>> impacts the scale of the raw channels. Eg, doubling the gain will double
>> the values read from the raw channels, which halves the scale value. The
>> integration time can also be set for the sensor. This does also have an
>> impact to the scale of the intensity channels because increasing the
>> integration time will also increase the values reported via the raw
>> channels.
>>
>> Impact of integration time to the scale and the fact that the scale value
>> does not start from '1', can make it hard for a human reader to compute the
>> gain values based on the scale.
>>
>> Add read-only HARDWAREGAIN to help debugging.
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> Other than the thing the bot found with fallthrough on the switch statement
> not being marked LGTM.
>> ---
>>   drivers/iio/light/rohm-bu27034.c | 14 +++++++++++++-
>>   1 file changed, 13 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/light/rohm-bu27034.c b/drivers/iio/light/rohm-bu27034.c
>> index 51acad2cafbd..b299ff2aacce 100644
>> --- a/drivers/iio/light/rohm-bu27034.c
>> +++ b/drivers/iio/light/rohm-bu27034.c
>> @@ -149,7 +149,8 @@ static const struct iio_itime_sel_mul bu27034_itimes[] = {
>>   	.channel = BU27034_CHAN_##_name,				\
>>   	.channel2 = IIO_MOD_LIGHT_CLEAR,				\
>>   	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
>> -			      BIT(IIO_CHAN_INFO_SCALE),			\
>> +			      BIT(IIO_CHAN_INFO_SCALE) |		\
>> +			      BIT(IIO_CHAN_INFO_HARDWAREGAIN),		\
>>   	.info_mask_separate_available = BIT(IIO_CHAN_INFO_SCALE),	\
>>   	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),		\
>>   	.info_mask_shared_by_all_available =				\
>> @@ -992,6 +993,13 @@ static int bu27034_read_raw(struct iio_dev *idev,
>>   
>>   		return IIO_VAL_INT_PLUS_MICRO;
>>   
>> +	case IIO_CHAN_INFO_HARDWAREGAIN:
>> +		ret = bu27034_get_gain(data, chan->channel, val);
>> +		if (ret)
>> +			return ret;
>> +
>> +		return IIO_VAL_INT;
>> +
>>   	case IIO_CHAN_INFO_SCALE:
>>   		return bu27034_get_scale(data, chan->channel, val, val2);
>>   
>> @@ -1036,12 +1044,16 @@ static int bu27034_write_raw_get_fmt(struct iio_dev *indio_dev,
>>   				     struct iio_chan_spec const *chan,
>>   				     long mask)
>>   {
>> +	struct bu27034_data *data = iio_priv(indio_dev);
>>   
>>   	switch (mask) {
>>   	case IIO_CHAN_INFO_SCALE:
>>   		return IIO_VAL_INT_PLUS_NANO;
>>   	case IIO_CHAN_INFO_INT_TIME:
>>   		return IIO_VAL_INT_PLUS_MICRO;
>> +	case IIO_CHAN_INFO_HARDWAREGAIN:
>> +		dev_dbg(data->dev,
>> +			"HARDWAREGAIN is read-only, use scale to set\n");
> 
> return -EINVAL here.  You could use a fall through marking but it gains
> little so I wouldn't bother.

Right, thanks.

> 
>>   	default:
>>   		return -EINVAL;
>>   	}
> 

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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