[PATCH] video: Add parentheses around VNBYTES() macro

[Simon Glass]

Hi Tom, Dan,

On Tue, 8 Aug 2023 at 19:39, Tom Rini <trini at konsulko.com> wrote:
>
> On Wed, Jul 26, 2023 at 09:54:08AM +0300, Dan Carpenter wrote:
>
> > The VNBYTES() macro needs to have parentheses to prevent some (harmless)
> > macro expansion bugs.  The VNBYTES() macro is used like this:
> >
> >       VID_TO_PIXEL(x) * VNBYTES(vid_priv->bpix)
> >
> > The * operation is done before the / operation.  It still ends up with
> > the same results, but it's not ideal.
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter at linaro.org>
> > Reviewed-by: Simon Glass <sjg at chromium.org>
>
> In that this seems correct:
>
> Applied to u-boot/next, thanks!
>
> But I want to note that with gcc-13.1 (and binutils 2.40) or more
> specifically the kernel.org arm/aarch64/etc toolchains, this causes the
> generated code to change:
>    aarch64: (for 1/1 boards) all +8.0 text +8.0
>             bananapi-m5    : all +8 text +8
>                u-boot: add: 0/0, grow: 1/0 bytes: 8/0 (8)
>                  function                                   old     new   delta
>                  video_post_probe                           248     256      +8
>
> So I don't know that this was a harmless bug.

Hmm I should have read the comment directly above...

"Note we omit the outer brackets to allow multiplication by fractional pixels."

Having said that, it doesn't seem to matter getting (if indeed we do)
a less accurate result.

Regards,
Simon