linux-kernel - Re: [PATCH v2 5/9] iio: inkern: Add a helper to query an available minimum raw value

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Date:   Mon, 5 Jun 2023 09:46:37 +0200
From:   Herve Codina <herve.codina@...tlin.com>
To:     andy.shevchenko@...il.com
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 5/9] iio: inkern: Add a helper to query an available
 minimum raw value

On Sat, 3 Jun 2023 17:04:37 +0300
andy.shevchenko@...il.com wrote:

> Tue, May 23, 2023 at 05:12:19PM +0200, Herve Codina kirjoitti:
> > A helper, iio_read_max_channel_raw() exists to read the available
> > maximum raw value of a channel but nothing similar exists to read the
> > available minimum raw value.
> > 
> > This new helper, iio_read_min_channel_raw(), fills the hole and can be
> > used for reading the available minimum raw value of a channel.
> > It is fully based on the existing iio_read_max_channel_raw().  
> 
> ...
> 
> > +static int iio_channel_read_min(struct iio_channel *chan,
> > +				int *val, int *val2, int *type,
> > +				enum iio_chan_info_enum info)
> > +{
> > +	int unused;
> > +	const int *vals;
> > +	int length;
> > +	int ret;  
> 
> > +	if (!val2)
> > +		val2 = &unused;  
> 
> It's a single place, where this is used, can you move it there?

I will do that in the next iteration.
Also, I will do the same modification in iio_channel_read_max() as it has
exactly the same code.

> 
> > +	ret = iio_channel_read_avail(chan, &vals, type, &length, info);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	switch (ret) {
> > +	case IIO_AVAIL_RANGE:
> > +		switch (*type) {
> > +		case IIO_VAL_INT:
> > +			*val = vals[0];
> > +			break;
> > +		default:
> > +			*val = vals[0];
> > +			*val2 = vals[1];
> > +		}
> > +		return 0;
> > +
> > +	case IIO_AVAIL_LIST:
> > +		if (length <= 0)
> > +			return -EINVAL;
> > +		switch (*type) {
> > +		case IIO_VAL_INT:
> > +			*val = vals[--length];  
> 
> > +			while (length) {  
> 
> 			while (length--) {
> 
> will do the job and at the same time...
> 
> 
> > +				if (vals[--length] < *val)
> > +					*val = vals[length];  
> 
> ...this construction becomes less confusing (easier to parse).

Indeed, I will change in the next iteration.

> 
> > +			}
> > +			break;
> > +		default:
> > +			/* FIXME: learn about min for other iio values */  
> 
> I believe in a final version this comment won't be here.

We have the same FIXME comment in the iio_channel_read_max() function I
copied to create this iio_channel_read_min() and, to be honest, I
don't really know how to handle these other cases.

In this series, I would prefer to keep this FIXME.

> 
> > +			return -EINVAL;
> > +		}
> > +		return 0;
> > +
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}  
> 

Thanks for the review,
Hervé