Re: [PATCH v2 3/5] media: mali-c55: Add Mali-C55 ISP driver

Laurent Pinchart
2024-02-28T13:39:00Z

On Wed, Feb 28, 2024 at 01:29:36PM +0000, Kieran Bingham wrote:
> Quoting Sakari Ailus (2024-02-28 13:11:39)
> > On Wed, Feb 28, 2024 at 01:50:14PM +0100, Jacopo Mondi wrote:
> > > > > +const struct mali_c55_fmt *mali_c55_cap_fmt_next(const struct mali_c55_fmt *fmt,
> > > > > + bool allow_raw, bool unique)
> > > > > +{
> > > > > + if (!fmt)
> > > > > + fmt = &mali_c55_fmts[0];
> > > > > + else
> > > > > + ++fmt;
> > > >
> > > > fmt++, please.
> > >
> > > Can I ask why ? (here and in the next occurrences you have reported)
> >
> > It's much, much more common and using that form makes the code easier to
> > read. The rest of the driver primarily uses variable++, too, AFAIR.
> >
> > So you should use ++variable only when you need it.
>
> I don't think this is a hot path, but I'll never forget my C tutor
> telling us how ++i is more efficient than i++ somewhere to do with the
> opcode ordering, and not having to make a copy [*1]
>
> Though I bet any clever optimising compiler could spot this anyway.
>
> [*1]. Whatever plausibility there is based on a 20 year old memory and
> should be verified elsewhere.

In C I wouldn't expect any practical difference. C++ is a different
matter, as the prefix and postfix operators can have different
implementations.

--
Regards,

Laurent Pinchart