Re: [PATCH] pinctrl: renesas: rzn1: Use for_each_child_of_node_scoped()

[Dan Carpenter <dan.carpenter@linaro.org>]

On Fri, May 31, 2024 at 11:19:26AM +0300, Andy Shevchenko wrote:
> On Fri, May 31, 2024 at 11:01 AM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> > On Thu, May 30, 2024 at 04:36:59PM +0300, Andy Shevchenko wrote:
> > > On Thu, May 30, 2024 at 2:52 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > > On Thu, May 30, 2024 at 11:26 AM Andy Shevchenko
> > > > <andy.shevchenko@gmail.com> wrote:
> > > > > Thu, May 30, 2024 at 11:19:29AM +0200, Geert Uytterhoeven kirjoitti:
> > > > > > Use the scoped variant of for_each_child_of_node() to simplify the code.
> > > > >
> > > > > I do not see the point of this patch. This makes code actually more
> > > > > complicated, and I'm not sure the code generation is the same and not worse.
> > > >
> > > > On arm32, a conversion to for_each_child_of_node_scoped() seems to
> > > > cost ca. 48 bytes of additional code.
> > > >
> > > > BTW, the same is true for cases where the conversion does simplify
> > > > cleanup.
> > > >
> > > > I checked "pinctrl: renesas: Use scope based of_node_put() cleanups",
> > > > and all but the conversions in *_dt_node_to_map() cost 48 bytes each.
> > >
> > > Yeah. so for the cases where there are no returns from inside the loop
> > > I prefer not to use _scoped.
> >
> > Eventually _scoped() loops will become the norm.  Leaving some unscoped
> > loops will be a fun surprise for the first person to introduce a return
> > -EINVAL.
> 
> It makes no sense when we have no return / goto semantics from inside
> of the loop. I don't know why we should do worse binary code for no
> benefit.

The compiler ought to be able to determine when the cleanup function is
not required and save those 48 bytes.  That's why we have NULL checking
in __free_device_node() instead of using the NULL check in of_node_put().
The compiler is already removing all the calls from the return
statements where p is NULL.  It seems like a small thing to one step
further and delete the cleanup when it's not called on any path?

regards,
dan carpenter