[RESEND PATCH v5 3/5] drivers core: allow probe_err accept integer and pointer types

Andy Shevchenko andy.shevchenko at gmail.com
Wed Jun 24 08:55:57 EDT 2020

On Wed, Jun 24, 2020 at 3:37 PM Robin Murphy <robin.murphy at arm.com> wrote:
> On 2020-06-24 12:41, Andrzej Hajda wrote:
> > Many resource acquisition functions return error value encapsulated in
> > pointer instead of integer value. To simplify coding we can use macro
> > which will accept both types of error.
> > With this patch user can use:
> >       probe_err(dev, ptr, ...)
> > instead of:
> >       probe_err(dev, PTR_ERR(ptr), ...)
> > Without loosing old functionality:
> >       probe_err(dev, err, ...)
> Personally I'm not convinced that simplification has much value, and I'd
> say it *does* have a significant downside. This:
>         if (IS_ERR(x))
>                 do_something_with(PTR_ERR(x));
> is a familiar and expected pattern when reading/reviewing code, and at a
> glance is almost certainly doing the right thing. If I see this, on the
> other hand:
>         if (IS_ERR(x))
>                 do_something_with(x);

I don't consider your arguments strong enough. You are appealing to
one pattern vs. new coming *pattern* just with a different name and
actually much less characters to parse. We have a lot of clean ups
like this, have you protested against them? JFYI: they are now
*established patterns* and saved a ton of LOCs in some of which even
were typos.

> my immediate instinct is to be suspicious, and now I've got to go off
> and double-check that if do_something_with() really expects a pointer
> it's also robust against PTR_ERR values. Off-hand I can't think of any
> APIs that work that way in the areas with which I'm familiar, so it
> would be a pretty unusual and non-obvious thing.

With Best Regards,
Andy Shevchenko

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