Re: [PATCH 04/11] staging: iio: adt7316: fix handling of dac high resolution option

From: Dan Carpenter
Date: Fri Dec 14 2018 - 01:27:31 EST

On Thu, Dec 13, 2018 at 03:01:46PM -0700, Jeremy Fertic wrote:
> On Wed, Dec 12, 2018 at 11:23:16AM +0300, Dan Carpenter wrote:
> > On Tue, Dec 11, 2018 at 05:54:56PM -0700, Jeremy Fertic wrote:
> > > @@ -651,10 +649,12 @@ static ssize_t adt7316_store_da_high_resolution(struct device *dev,
> > > u8 config3;
> > > int ret;
> > >
> > > + if (chip->id == ID_ADT7318 || chip->id == ID_ADT7519)
> > > + return -EPERM;
> >
> > return -EINVAL is more appropriate than -EPERM.
> >
> > regards,
> > dan carpenter
> >
> I chose -EPERM because the driver uses it quite a few times in similar
> circumstances.

Yeah. I saw that when I reviewed the later patches in this series.

It's really not doing it right. -EPERM means permission checks like
access_ok() failed so it's not appropriate. -EINVAL is sort of general
purpose for invalid commands so it's probably the correct thing.

> At least with this driver, -EINVAL is used when the user
> attempts to write data that would never be valid. -EPERM is used when
> either the current device settings prevent some functionality from being
> used, or the device never supports that functionality. This patch is the
> latter, that these two chip ids never support this function.
> I'll change to -EINVAL in a v2 series, but I wonder if I should hold off
> on a separate patch for other instances in this driver since it will be
> undergoing a substantial refactoring.

Generally, you should prefer kernel standards over driver standards and
especially for staging. But it doesn't matter. When I reviewed this
patch, I hadn't seen that the driver was doing it like this but now I
know so it's fine. We can clean it all at once later if you want.

dan carpenter