[PATCH] pinctrl: renesas: no need to initialise global statics

[PATCH] pinctrl: renesas: no need to initialise global statics

[Jason Wang]

Global static variables dont need to be initialised to 0. Because
the compiler will initialise them.

Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
---
 drivers/pinctrl/renesas/core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/pinctrl/renesas/core.c b/drivers/pinctrl/renesas/core.c
index f2ab02225837..ef8ef05ba930 100644
--- a/drivers/pinctrl/renesas/core.c
+++ b/drivers/pinctrl/renesas/core.c
@@ -741,12 +741,12 @@ static int sh_pfc_suspend_init(struct sh_pfc *pfc) { return 0; }
 #define SH_PFC_MAX_REGS		300
 #define SH_PFC_MAX_ENUMS	3000
 
-static unsigned int sh_pfc_errors __initdata = 0;
-static unsigned int sh_pfc_warnings __initdata = 0;
-static u32 *sh_pfc_regs __initdata = NULL;
-static u32 sh_pfc_num_regs __initdata = 0;
-static u16 *sh_pfc_enums __initdata = NULL;
-static u32 sh_pfc_num_enums __initdata = 0;
+static unsigned int sh_pfc_errors __initdata;
+static unsigned int sh_pfc_warnings __initdata;
+static u32 *sh_pfc_regs __initdata;
+static u32 sh_pfc_num_regs __initdata;
+static u16 *sh_pfc_enums __initdata;
+static u32 sh_pfc_num_enums __initdata;
 
 #define sh_pfc_err(fmt, ...)					\
 	do {							\
-- 
2.33.0

Re: [PATCH] pinctrl: renesas: no need to initialise global statics

[Geert Uytterhoeven]

Hi Jason,

On Mon, Sep 6, 2021 at 3:41 PM Jason Wang <wangborong@cdjrlc.com> wrote:
> Global static variables dont need to be initialised to 0. Because
> the compiler will initialise them.
>
> Signed-off-by: Jason Wang <wangborong@cdjrlc.com>

Thanks for your patch!

> --- a/drivers/pinctrl/renesas/core.c
> +++ b/drivers/pinctrl/renesas/core.c
> @@ -741,12 +741,12 @@ static int sh_pfc_suspend_init(struct sh_pfc *pfc) { return 0; }
>  #define SH_PFC_MAX_REGS                300
>  #define SH_PFC_MAX_ENUMS       3000
>
> -static unsigned int sh_pfc_errors __initdata = 0;
> -static unsigned int sh_pfc_warnings __initdata = 0;
> -static u32 *sh_pfc_regs __initdata = NULL;
> -static u32 sh_pfc_num_regs __initdata = 0;
> -static u16 *sh_pfc_enums __initdata = NULL;
> -static u32 sh_pfc_num_enums __initdata = 0;
> +static unsigned int sh_pfc_errors __initdata;
> +static unsigned int sh_pfc_warnings __initdata;
> +static u32 *sh_pfc_regs __initdata;
> +static u32 sh_pfc_num_regs __initdata;
> +static u16 *sh_pfc_enums __initdata;
> +static u32 sh_pfc_num_enums __initdata;

These are special, as they use __initdata.
While dropping the initializers seems to work fine with e.g. gcc 9,
I'm quite sure that would fail with older compiler versions, where
the variable would be put in bss instead of initdata.

See the example in include/linux/init.h, which explicitly
initializes a variable with zero:

    static int init_variable __initdata = 0;

Arnd: do you know in which version of gcc this was fixed?
It seems at least 6.5.0 and later are fine (I don't have all required
shared libs to run e.g. 5.5.0).

>  #define sh_pfc_err(fmt, ...)                                   \
>         do {                                                    \

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] pinctrl: renesas: no need to initialise global statics

[Arnd Bergmann]

On Mon, Sep 6, 2021 at 4:36 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > --- a/drivers/pinctrl/renesas/core.c
> > +++ b/drivers/pinctrl/renesas/core.c
> > @@ -741,12 +741,12 @@ static int sh_pfc_suspend_init(struct sh_pfc *pfc) { return 0; }
> >  #define SH_PFC_MAX_REGS                300
> >  #define SH_PFC_MAX_ENUMS       3000
> >
> > -static unsigned int sh_pfc_errors __initdata = 0;
> > -static unsigned int sh_pfc_warnings __initdata = 0;
> > -static u32 *sh_pfc_regs __initdata = NULL;
> > -static u32 sh_pfc_num_regs __initdata = 0;
> > -static u16 *sh_pfc_enums __initdata = NULL;
> > -static u32 sh_pfc_num_enums __initdata = 0;
> > +static unsigned int sh_pfc_errors __initdata;
> > +static unsigned int sh_pfc_warnings __initdata;
> > +static u32 *sh_pfc_regs __initdata;
> > +static u32 sh_pfc_num_regs __initdata;
> > +static u16 *sh_pfc_enums __initdata;
> > +static u32 sh_pfc_num_enums __initdata;
>
> These are special, as they use __initdata.
> While dropping the initializers seems to work fine with e.g. gcc 9,
> I'm quite sure that would fail with older compiler versions, where
> the variable would be put in bss instead of initdata.
>
> See the example in include/linux/init.h, which explicitly
> initializes a variable with zero:
>
>     static int init_variable __initdata = 0;
>
> Arnd: do you know in which version of gcc this was fixed?
> It seems at least 6.5.0 and later are fine (I don't have all required
> shared libs to run e.g. 5.5.0).

I think you mixed up what happens: As far as I know, older compilers
would put variables without the =0 into .bss, but those with the explicit
=0 would end up in .data. Newer compilers treat them exactly the
same, and these variables all get put into .bss by default. This seems
to already be the case with gcc-4.1, which is the oldest one I could
easily try.

I'm rather sure that regardless of the compiler version, adding an
explicit section attribute like the __initdata would force the section
even on the pre-4.1 compilers.

        Arnd

Re: [PATCH] pinctrl: renesas: no need to initialise global statics

[Geert Uytterhoeven]

On Mon, Sep 6, 2021 at 5:18 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Sep 6, 2021 at 4:36 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > --- a/drivers/pinctrl/renesas/core.c
> > > +++ b/drivers/pinctrl/renesas/core.c
> > > @@ -741,12 +741,12 @@ static int sh_pfc_suspend_init(struct sh_pfc *pfc) { return 0; }
> > >  #define SH_PFC_MAX_REGS                300
> > >  #define SH_PFC_MAX_ENUMS       3000
> > >
> > > -static unsigned int sh_pfc_errors __initdata = 0;
> > > -static unsigned int sh_pfc_warnings __initdata = 0;
> > > -static u32 *sh_pfc_regs __initdata = NULL;
> > > -static u32 sh_pfc_num_regs __initdata = 0;
> > > -static u16 *sh_pfc_enums __initdata = NULL;
> > > -static u32 sh_pfc_num_enums __initdata = 0;
> > > +static unsigned int sh_pfc_errors __initdata;
> > > +static unsigned int sh_pfc_warnings __initdata;
> > > +static u32 *sh_pfc_regs __initdata;
> > > +static u32 sh_pfc_num_regs __initdata;
> > > +static u16 *sh_pfc_enums __initdata;
> > > +static u32 sh_pfc_num_enums __initdata;
> >
> > These are special, as they use __initdata.
> > While dropping the initializers seems to work fine with e.g. gcc 9,
> > I'm quite sure that would fail with older compiler versions, where
> > the variable would be put in bss instead of initdata.
> >
> > See the example in include/linux/init.h, which explicitly
> > initializes a variable with zero:
> >
> >     static int init_variable __initdata = 0;
> >
> > Arnd: do you know in which version of gcc this was fixed?
> > It seems at least 6.5.0 and later are fine (I don't have all required
> > shared libs to run e.g. 5.5.0).
>
> I think you mixed up what happens: As far as I know, older compilers
> would put variables without the =0 into .bss, but those with the explicit
> =0 would end up in .data. Newer compilers treat them exactly the
> same, and these variables all get put into .bss by default. This seems
> to already be the case with gcc-4.1, which is the oldest one I could
> easily try.
>
> I'm rather sure that regardless of the compiler version, adding an
> explicit section attribute like the __initdata would force the section
> even on the pre-4.1 compilers.

I must be misremembering...

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
i.e. will queue in renesas-pinctrl-for-v5.16.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds