linux-kernel - Re: [PATCH 1/2] pinctrl: pinconf-generic: resize the pin config array directly

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Message-ID: <CACRpkdaMBrWUR8OYLPiQNNJ64mfenFyQa9f4iB+w5kZ44WjSeQ@mail.gmail.com>
Date:   Fri, 24 Nov 2023 11:06:50 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] pinctrl: pinconf-generic: resize the pin config array directly

Hi Masahiro,

On Tue, Nov 21, 2023 at 11:21 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> On Tue, Nov 21, 2023 at 7:28 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > pinconf_generic_parse_dt_config() allocates memory that is large enough
> > to contain all the config parameters. Then, kmemdup() copies the found
> > configs to the memory with the exact size.
> >
> > There is no need to allocate memory twice; you can directly resize the
> > initial memory using krealloc_array().
> >
> > I also changed kcalloc() to kmalloc_array() to keep the consistency with
> > krealloc_array(). This change has no impact because you do not need to
> > zero out the 'cfg' array.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>
> Sorry, I retract this patch set.
>
> krealloc() does not save any memory
> when the new_size is smaller than the current size.

But the first part where you switch to kmalloc_array() is still a nice change.

The fact that we use kmemdup to be able to also shrink the allocation is a
bit of an oddity I guess, but let's run this patch by Andy Shevchenko, and
ask what he thinks about simply introducing kmemdup_array() or if he
has other ideas for this.

Yours,
Linus Walleij