linux-kernel - Re: [PATCH 1/4] iio: inkern: Remove useless argument to iio_channel_read

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Date:   Sun, 31 Jul 2022 18:07:13 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Peter Rosin <peda@...ntia.se>,
        Lars-Peter Clausen <lars@...afoo.de>, list@...ndingux.net,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] iio: inkern: Remove useless argument to
 iio_channel_read_max()

On Thu, 21 Jul 2022 20:15:23 +0100
Paul Cercueil <paul@...pouillou.net> wrote:

> The 'type' argument was passed by the only caller of the
> iio_channel_read_max() function as a pointer to return an extra value,
> but the value of the variable passed by the caller was never read
> afterwards.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>

Curious. I'm playing guess the intent here and I suspect that what
we should really be doing is checking type in 
iio_read_max_channel_raw() and returning an error if it is not IIO_VAL_INT
(can only get there for IIO_AVAIL_RANGE currently as there is a FIXME for
 IIO_AVAIL_LIST for non IIO_VAL_INT types)

I'm not sure we've ever documented that _RAW can't be non integer even if
that makes relatively little sense most of the time..

Jonathan

> ---
>  drivers/iio/inkern.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index df74765d33dc..e8a25852f0df 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -813,21 +813,22 @@ int iio_read_avail_channel_raw(struct iio_channel *chan,
>  EXPORT_SYMBOL_GPL(iio_read_avail_channel_raw);
>  
>  static int iio_channel_read_max(struct iio_channel *chan,
> -				int *val, int *val2, int *type,
> +				int *val, int *val2,
>  				enum iio_chan_info_enum info)
>  {
>  	int unused;
>  	const int *vals;
>  	int length;
>  	int ret;
> +	int type;
>  
>  	if (!val2)
>  		val2 = &unused;
>  
> -	ret = iio_channel_read_avail(chan, &vals, type, &length, info);
> +	ret = iio_channel_read_avail(chan, &vals, &type, &length, info);
>  	switch (ret) {
>  	case IIO_AVAIL_RANGE:
> -		switch (*type) {
> +		switch (type) {
>  		case IIO_VAL_INT:
>  			*val = vals[2];
>  			break;
> @@ -840,7 +841,7 @@ static int iio_channel_read_max(struct iio_channel *chan,
>  	case IIO_AVAIL_LIST:
>  		if (length <= 0)
>  			return -EINVAL;
> -		switch (*type) {
> +		switch (type) {
>  		case IIO_VAL_INT:
>  			*val = vals[--length];
>  			while (length) {
> @@ -863,7 +864,6 @@ int iio_read_max_channel_raw(struct iio_channel *chan, int *val)
>  {
>  	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(chan->indio_dev);
>  	int ret;
> -	int type;
>  
>  	mutex_lock(&iio_dev_opaque->info_exist_lock);
>  	if (!chan->indio_dev->info) {
> @@ -871,7 +871,7 @@ int iio_read_max_channel_raw(struct iio_channel *chan, int *val)
>  		goto err_unlock;
>  	}
>  
> -	ret = iio_channel_read_max(chan, val, NULL, &type, IIO_CHAN_INFO_RAW);
> +	ret = iio_channel_read_max(chan, val, NULL, IIO_CHAN_INFO_RAW);
>  err_unlock:
>  	mutex_unlock(&iio_dev_opaque->info_exist_lock);
>