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SubjectRe: [PATCH v2 3/8] iio: inkern: error out on unsupported offset type
On Mon,  7 Jun 2021 10:47:13 -0400
Liam Beguin <liambeguin@gmail.com> wrote:

> From: Liam Beguin <lvb@xiphos.com>
>
> iio_convert_raw_to_processed_unlocked() assumes the offset is an
> integer.
> Make that clear to the consumer by returning an error on unsupported
> offset types without breaking valid implicit truncations.
>
> Signed-off-by: Liam Beguin <lvb@xiphos.com>
> ---
> drivers/iio/inkern.c | 34 +++++++++++++++++++++++++++++-----
> 1 file changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index b69027690ed5..0b5667f22b1d 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -578,13 +578,37 @@ EXPORT_SYMBOL_GPL(iio_read_channel_average_raw);
> static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
> int raw, int *processed, unsigned int scale)
> {
> - int scale_type, scale_val, scale_val2, offset;
> + int scale_type, scale_val, scale_val2;
> + int offset_type, offset_val, offset_val2;
> s64 raw64 = raw;
> - int ret;
>
> - ret = iio_channel_read(chan, &offset, NULL, IIO_CHAN_INFO_OFFSET);
> - if (ret >= 0)
> - raw64 += offset;
> + offset_type = iio_channel_read(chan, &offset_val, &offset_val2,
> + IIO_CHAN_INFO_OFFSET);
> + if (offset_type >= 0) {
> + switch (offset_type) {
> + case IIO_VAL_INT:
> + break;
> + case IIO_VAL_INT_PLUS_MICRO:
> + if (offset_val2 > 1000)

What's the logic behind this one? > 1000000
would be an interesting corner case, though I'm not sure we've ever
explicitly disallowed it before.

Why are we at 1000th of that for the check?

> + return -EINVAL;
> + break;
> + case IIO_VAL_INT_PLUS_NANO:
> + if (offset_val2 > 1000000)

Similar this is a bit odd.

> + return -EINVAL;
> + case IIO_VAL_FRACTIONAL:
> + if (offset_val2 != 1)
> + return -EINVAL;

We could be more flexible on this, but I don't recall any
channels using this so far.

> + break;
> + case IIO_VAL_FRACTIONAL_LOG2:
> + if (offset_val2)
> + return -EINVAL;

Same in this case.

> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + raw64 += offset_val;
> + }
>
> scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
> IIO_CHAN_INFO_SCALE);

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