Re: [PATCH v2] iio: core: register chardev only if needed

[Alexandru Ardelean]

On Sun, Dec 13, 2020 at 4:31 PM Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>
> On Wed, 9 Dec 2020 17:55:22 +0200
> Alexandru Ardelean <ardeleanalex@xxxxxxxxx> wrote:
>
> > On Wed, Dec 9, 2020 at 5:53 PM Andy Shevchenko
> > <andy.shevchenko@xxxxxxxxx> wrote:
> > >
> > > On Wed, Dec 9, 2020 at 5:45 PM Alexandru Ardelean
> > > <ardeleanalex@xxxxxxxxx> wrote:
> > > > On Wed, Dec 9, 2020 at 5:37 PM Andy Shevchenko
> > > > <andy.shevchenko@xxxxxxxxx> wrote:
> > > > > On Thu, Dec 3, 2020 at 11:55 AM Alexandru Ardelean
> > > > > <alexandru.ardelean@xxxxxxxxxx> wrote:
> > >
> > > ...
> > >
> > > > > Are you sure there is no user space application that doesn't rely on
> > > > > character device to be always present?
> > > >
> > > > Nope.
> > > > I'm not sure.
> > > > I'm also not completely sure how Jonathan feels about this patch being
> > > > added now [so late].
> > > >
> > > > Though, technically if the chardev was already there, without all the
> > > > control in place [to enable IIO buffers and other stuff through the
> > > > chardev] then it's technically just a "marker" file.
> > > > Which arguably is a lot to have (i.e. chardev that should be unusable).
> > > >
> > > > If it is usable with no control in place for buffers or other stuff
> > > > (i.e. I missed something), then I also don't know.
> > > >
> > > > So, this patch on it's own can still be interpreted as an RFC.
> > > > See:
> > > > https://lore.kernel.org/linux-iio/20201121180246.772ad299@archlinux/
> > >
> > > Don't take me wrong, I'm not against a good change (I doesn't like
> > > dangling files), but it might break some use cases.
> >
> > Yeah I know.
> > But how else do you know if a dangling file might break some use cases?
> >
> > The worst that would happen is that we get a report and create a Fixes
> > tag and we know.
> > But if we don't try it, we're stuck with it, and will never know.
> >
> It's definitely a high risk change.  I'd 'hope' it's not a problem
> but we should do a bit more due diligence.
>
> I hope we can assume the ADI software is all fine with dropping this.
> Bastien can you see any issues with dropping chrdev for IIO devices
> that don't actually support using it for anything (sysfs interface only).
>
> What other stacks are people aware of that we should enquire about?

Hey,

Any more thoughts on this?

Thanks
Alex

>
> Thanks,
>
> Jonathan
> > >
> > > --
> > > With Best Regards,
> > > Andy Shevchenko
>