Re: [PATCH] iio: core: Fix mapping of iio channels to entry numbers

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 27 Jun 2017 09:46:01 -0700
Gaurav Gupta <gauragup@cisco.com> wrote:

> When adding maps to the list, they were added using list_add, which adds
> them in LIFO order. When parsing using iio_channel_get_all(), these
> elements are hence returned in reverse order. As a result, the iio_hwmon
> mapping maps the first entry to the last channel and so on.
> 
> Signed-off-by: Gaurav Gupta <gauragup@cisco.com>
Gah.  This is one of those nasty cases where I clearly messed up a
long time ago, but unfortunately it's become user space ABI.

So looking for general opinions on whether we can fix this one
or not.  I can't immediately think of a clean way to tidy this up.

So do we think people will notice if we fix this?

Jonathan
> ---
>  drivers/iio/inkern.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 7a13535..9b0715c 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -44,7 +44,7 @@ int iio_map_array_register(struct iio_dev *indio_dev, struct iio_map *maps)
>  		}
>  		mapi->map = &maps[i];
>  		mapi->indio_dev = indio_dev;
> -		list_add(&mapi->l, &iio_map_list);
> +		list_add_tail(&mapi->l, &iio_map_list);
>  		i++;
>  	}
>  error_ret: