Re: [PATCH 2/4] iio: ensure scan index is unique at buffer register

[Hartmut Knaack <knaack.h@gmx.de>]

Vlad Dogaru wrote on 25.11.2014 13:48:
> Having two or more channels with the same positive scan_index field
> makes no sense.  Prevent this situation by failing to register a buffer
> if two scan indexes are identical.
> 
> Signed-off-by: Vlad Dogaru <vlad.dogaru@intel.com>
> ---
>  drivers/iio/industrialio-buffer.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index f971f79..422b29e 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -309,6 +309,30 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
>  	return ret;
>  }
>  
> +static int iio_check_unique_scan_index(struct iio_dev *indio_dev,
> +				       const struct iio_chan_spec *channels,
> +				       int num_channels)
> +{
> +	int i, j;
> +
> +	for (i = 0; i < num_channels - 1; i++) {
> +		if (channels[i].scan_index < 0)
> +			continue;
> +		for (j = i + 1; j < num_channels; j++) {
> +			if (channels[j].scan_index < 0)
> +				continue;
This check up here is unnecessary, since channels[i].scan_index is already equal or
greater zero, so the check below results in a false for channels[j].scan_index smaller
than zero and cause a new loop iteration anyway.

> +			if (channels[i].scan_index == channels[j].scan_index) {
> +				dev_err(&indio_dev->dev,
> +					"duplicate scan index %d\n",
> +					channels[i].scan_index);
> +				return -EINVAL;
> +			}
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static const char * const iio_scan_elements_group_name = "scan_elements";
>  
>  int iio_buffer_register(struct iio_dev *indio_dev,
> @@ -320,6 +344,10 @@ int iio_buffer_register(struct iio_dev *indio_dev,
>  	struct iio_buffer *buffer = indio_dev->buffer;
>  	int ret, i, attrn, attrcount, attrcount_orig = 0;
>  
> +	ret = iio_check_unique_scan_index(indio_dev, channels, num_channels);
> +	if (ret < 0)
> +		return ret;
> +
>  	if (buffer->attrs)
>  		indio_dev->groups[indio_dev->groupcounter++] = buffer->attrs;
>  
>