linux-kernel - Re: [PATCH v4 2/2] iio: light: ROHM BH1745 colour sensor

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Date: Mon, 17 Jun 2024 19:52:55 +0100
From: Mudit Sharma <muditsharma.info@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
 Jonathan Cameron <jic23@...nel.org>
Cc: lars@...afoo.de, krzk+dt@...nel.org, conor+dt@...nel.org,
 robh@...nel.org, ivan.orlov0322@...il.com, javier.carrasco.cruz@...il.com,
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v4 2/2] iio: light: ROHM BH1745 colour sensor

On 10/06/2024 06:58, Matti Vaittinen wrote:
> la 8. kesäk. 2024 klo 19.22 Jonathan Cameron (jic23@...nel.org) kirjoitti:
>>
>> On Thu,  6 Jun 2024 17:29:42 +0100
>> Mudit Sharma <muditsharma.info@...il.com> wrote:
>>
>>> Add support for BH1745, which is an I2C colour sensor with red, green,
>>> blue and clear channels. It has a programmable active low interrupt
>>> pin. Interrupt occurs when the signal from the selected interrupt
>>> source channel crosses set interrupt threshold high or low level.
>>>
>>> This driver includes device attributes to configure the following:
>>> - Interrupt pin latch: The interrupt pin can be configured to
>>>    be latched (until interrupt register (0x60) is read or initialized)
>>>    or update after each measurement.
>>> - Interrupt source: The colour channel that will cause the interrupt
>>>    when channel will cross the set threshold high or low level.
>>>
>>> This driver also includes device attributes to present valid
>>> configuration options/values for:
>>> - Integration time
>>> - Interrupt colour source
>>> - Hardware gain
>>>
> 
>>> +
>>> +#define BH1745_CHANNEL(_colour, _si, _addr)                                   \
>>> +     {                                                                     \
>>> +             .type = IIO_INTENSITY, .modified = 1,                         \
>>> +             .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),                 \
>>> +             .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_HARDWAREGAIN) | \
>>
>> Provide _SCALE instead of HARDWAREGAIN
>> As it's an intensity channel (and units are tricky for color sensors given
>> frequency dependence etc) all you need to do is ensure that if you halve
>> the _scale and measure the same light source, the computed
>> _RAW * _SCALE value remains constant.
> 
> ...Which is likely to cause also the integration time setting to
> impact the SCALE.
> 
> You may or may not want to see the GTS-helpers
> (drivers/iio/industrialio-gts-helper.c) - which have their own tricky
> corners. I think Jonathan once suggested to me to keep the

Hi Matti,

Thank you for the recommendation here.

Looking into GTS-helper for v5.

Best regards,
Mudit Sharma