linux-kernel - Re: [PATCH v6 2/2] iio: light: ROHM BH1745 colour sensor

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Date: Sat, 29 Jun 2024 10:10:19 +0100
From: Mudit Sharma <muditsharma.info@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: lars@...afoo.de, krzk+dt@...nel.org, conor+dt@...nel.org,
 robh@...nel.org, linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, Ivan Orlov <ivan.orlov0322@...il.com>,
 Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: Re: [PATCH v6 2/2] iio: light: ROHM BH1745 colour sensor

On 28/06/2024 20:37, Jonathan Cameron wrote:
> Hi Mudit,
> 
> I'd failed on previous reviews to notice the odd trigger in here.
> What is it, because it doesn't seem to be a dataready trigger as the device
> doesn't seem to provide such an interrupt?

Hi Jonathan,

Thank you for your review on this.

I've incorrect called it as a dataready trigger, I missed this as part 
of my initial cleanup - apologies for the confusion caused by this. I 
should potentially call it 'threshold' or 'dev'. Please suggest what you 
think would be appropriate here.

The sensor has an active low interrupt pin which is connected to a GPIO 
(input, pullup). When the sensor reading crosses value set in threshold 
high or threshold low resisters, interrupt signal is generated and the 
interrupt gets handled in 'bh1745_interrupt_handler()' (interrupt also 
depends on number of consecutive judgements set in BH1745_PERSISTENCE 
register)

> 
> Various other comments inline.

Will address all for v7
>
...
>> +static irqreturn_t bh1745_interrupt_handler(int interrupt, void *p)
>> +{
>> +	struct iio_dev *indio_dev = p;
>> +	struct bh1745_data *data = iio_priv(indio_dev);
>> +	int ret;
>> +	int value;
>> +
>> +	ret = regmap_read(data->regmap, BH1745_INTR, &value);
>> +	if (ret)
>> +		return IRQ_NONE;
>> +
>> +	if (value & BH1745_INTR_STATUS) {
>> +		guard(mutex)(&data->lock);
>> +		iio_push_event(indio_dev,
>> +			       IIO_UNMOD_EVENT_CODE(IIO_INTENSITY, data->int_src,
>> +						    IIO_EV_TYPE_THRESH,
>> +						    IIO_EV_DIR_EITHER),
>> +			       iio_get_time_ns(indio_dev));
> 
> What is happening here.  You always push out the event and use that as
> a trigger?  This is an unusual trigger if it's appropriate to use it for
> one at all.  You've called it a dataready trigger but it is not obvious
> that this device provides any such signal.

When an interrupt occurs, BH1745_INTR_STATUS bit is set in the 
BH1745_INTR register. Event is only pushed out when the 
BH1745_INTR_STATUS bit is set.
>> +
>> +		iio_trigger_poll_nested(data->trig);
>> +
>> +		return IRQ_HANDLED;
>> +	}
>> +
>> +	return IRQ_NONE;
>> +}

Best regards,
Mudit Sharma