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Date: Thu, 2 May 2024 21:17:56 +0200
From: Marek =?utf-8?B?QmVow7pu?= <kabel@kernel.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Gregory CLEMENT <gregory.clement@bootlin.com>,
	Arnd Bergmann <arnd@arndb.de>, soc@kernel.org, arm@kernel.org,
	Hans de Goede <hdegoede@redhat.com>,
	Ilpo =?utf-8?B?SsOkcnZpbmVu?= <ilpo.jarvinen@linux.intel.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <brgl@bgdev.pl>, linux-gpio@vger.kernel.org,
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	linux-rtc@vger.kernel.org,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Guenter Roeck <linux@roeck-us.net>, linux-watchdog@vger.kernel.org
Subject: Re: [PATCH v8 2/9] platform: cznic: Add preliminary support for
 Turris Omnia MCU
Message-ID: <20240502191756.ynwmp74yybat57my@kandell>
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In-Reply-To: <CAHp75VfktKyGUNBz18TUQknF-5YZDOTgh2WLJhTs-_Ay-wgQoA@mail.gmail.com>

On Thu, May 02, 2024 at 09:47:25PM +0300, Andy Shevchenko wrote:
> On Thu, May 2, 2024 at 9:40 PM Marek Behún <kabel@kernel.org> wrote:
> > On Tue, Apr 30, 2024 at 06:17:45PM +0300, Andy Shevchenko wrote:
> > > On Tue, Apr 30, 2024 at 04:05:07PM +0200, Marek Behún wrote:
> > > > On Tue, 30 Apr 2024 15:53:51 +0300
> > > > Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> > > > > On Tue, Apr 30, 2024 at 2:51 PM Marek Behún <kabel@kernel.org> wrote:
> 
> ...
> 
> > > > > > +static int omnia_get_version_hash(struct omnia_mcu *mcu, bool bootloader,
> > > > > > +                                 u8 version[static OMNIA_FW_VERSION_HEX_LEN])
> > > > >
> > > > > Interesting format of the last parameter. Does it make any difference
> > > > > to the compiler if you use u8 *version?
> > > >
> > > > The compiler will warn if an array with not enough space is passed as
> > > > argument.
> > >
> > > Really?
> >
> > Indeed:
> >
> >   extern void a(char *x);
> >
> >   static void b(char x[static 10]) {
> >       a(x);
> >   }
> >
> >   void c(void) {
> >       char x[5] = "abcd";
> 
> >       b(x);
> 
> It's not the example I was talking about. Here should be a(x).

Somehow I got lost. Let's return to my function, where I have
  int omnia_get_version_hash(..., u8 version[static 40]);

and then I use this function:

  u8 version[40];
  omnia_get_version_hash(..., version);

If somehow I made a mistake and declared the version array shorter:
  u8 version[20];
  omnia_get_version_hash(..., version);
I would get a warning.

So the purpose is to get warned if the compiler can prove that there is
not enough space in the destination buffer.

Marek