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SubjectRe: [PATCH v7 4/5] iio: light: ROHM BU27034 Ambient Light Sensor
From
On 4/8/23 14:21, Jonathan Cameron wrote:
> On Fri, 31 Mar 2023 15:41:58 +0300
> Matti Vaittinen <mazziesaccount@gmail.com> wrote:
>
>> ROHM BU27034 is an ambient light sensor with 3 channels and 3 photo diodes
>> capable of detecting a very wide range of illuminance. Typical application
>> is adjusting LCD and backlight power of TVs and mobile phones.
>>
>> Add initial support for the ROHM BU27034 ambient light sensor.
>>
>> NOTE:
>> - Driver exposes 4 channels. One IIO_LIGHT channel providing the
>> calculated lux values based on measured data from diodes #0 and
>> #1. In addition, 3 IIO_INTENSITY channels are emitting the raw
>> register data from all diodes for more intense user-space
>> computations.
>> - Sensor has GAIN values that can be adjusted from 1x to 4096x.
>> - Sensor has adjustible measurement times of 5, 55, 100, 200 and
>> 400 mS. Driver does not support 5 mS which has special
>> limitations.
>> - Driver exposes standard 'scale' adjustment which is
>> implemented by:
>> 1) Trying to adjust only the GAIN
>> 2) If GAIN adjustment alone can't provide requested
>> scale, adjusting both the time and the gain is
>> attempted.
>> - Driver exposes writable INT_TIME property that can be used
>> for adjusting the measurement time. Time adjustment will also
>> cause the driver to try to adjust the GAIN so that the
>> overall scale is kept as close to the original as possible.
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
>
> A few trivial comments inline but nothing that stops me applying this version.
>
>>
>> +static int bu27034_read_raw(struct iio_dev *idev,
>> + struct iio_chan_spec const *chan,
>> + int *val, int *val2, long mask)
>> +{
>> + struct bu27034_data *data = iio_priv(idev);
>> + int ret;
>> +
>> + switch (mask) {
>> + case IIO_CHAN_INFO_INT_TIME:
>> + *val = bu27034_get_int_time(data);
>> + if (*val < 0)
>> + return *val;
>> +
>> + return IIO_VAL_INT;
>> +
>> + case IIO_CHAN_INFO_SCALE:
>> + return bu27034_get_scale(data, chan->channel, val, val2);
>> +
>> + case IIO_CHAN_INFO_RAW:
>> + {
>> + int (*result_get)(struct bu27034_data *data, int chan, int *val);
>
> I don't care that much about this, but the function pointer dance seems
> unnecessary.

My memory is getting worse and worse over the time... It's hard for me
to remember why I added a function pointer here - but it probably was to
keep the if-else if-else construct out of the mutex-protected section.

>
> You could probably also drop the paranoid checking (or default to one of the
> choices).

If this was done, then the function-pointer had no use. If you think the
check is paranoid, then I agree, we should go with the suggestion you
have below.

>
> So at call sight of result_get() currently have
> if (chan->type == IIO_INTENSITY)
> ret = bu27034_get_single-result()...
> else
> ret = bu27034_get_mlux()
>
> etc
>
> meh. I didn't raise it earlier so I'll leave this alone.
>
>> +
>> + if (chan->type == IIO_INTENSITY)
>> + result_get = bu27034_get_single_result;
>> + else if (chan->type == IIO_LIGHT)
>> + result_get = bu27034_get_mlux;
>> + else
>> + return -EINVAL;
>> +
>> + /* Don't mess with measurement enabling while buffering */
>> + ret = iio_device_claim_direct_mode(idev);
>> + if (ret)
>> + return ret;
>> +
>> + mutex_lock(&data->mutex);
>> + /*
>> + * Reading one channel at a time is inefficient but we
>> + * don't care here. Buffered version should be used if
>> + * performance is an issue.
>> + */
>> + ret = result_get(data, chan->channel, val);
>> +
>> + mutex_unlock(&data->mutex);
>> + iio_device_release_direct_mode(idev);
>> +
>> + if (ret)
>> + return ret;
>> +
>> + return IIO_VAL_INT;
>> + }
>> + default:
>> + return -EINVAL;
>> +
>> + }
>> +}
>
> I will fix the excess blank line above though. Serves no purpose
> so gone in the version I applied.

Thanks!

Yours,
-- Matti

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

~~ When things go utterly wrong vim users can always type :help! ~~

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