[PATCH] sh: clk: Fix discarding const qualifier warning

[PATCH] sh: clk: Fix discarding const qualifier warning

[Krzysztof Kozlowski]

ioreadX() accepts pointer to non-const memory.  This fixes warnings
like:

    drivers/sh/clk/cpg.c: In function ‘r8’:
    drivers/sh/clk/cpg.c:41:17: warning: passing argument 1 of ‘ioread8’
        discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
---
 drivers/sh/clk/cpg.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/sh/clk/cpg.c b/drivers/sh/clk/cpg.c
index eeb028b9cdb3..4f3d99d37809 100644
--- a/drivers/sh/clk/cpg.c
+++ b/drivers/sh/clk/cpg.c
@@ -36,17 +36,17 @@ static void sh_clk_write(int value, struct clk *clk)
 		iowrite32(value, clk->mapped_reg);
 }
 
-static unsigned int r8(const void __iomem *addr)
+static unsigned int r8(void __iomem *addr)
 {
 	return ioread8(addr);
 }
 
-static unsigned int r16(const void __iomem *addr)
+static unsigned int r16(void __iomem *addr)
 {
 	return ioread16(addr);
 }
 
-static unsigned int r32(const void __iomem *addr)
+static unsigned int r32(void __iomem *addr)
 {
 	return ioread32(addr);
 }
@@ -55,7 +55,7 @@ static int sh_clk_mstp_enable(struct clk *clk)
 {
 	sh_clk_write(sh_clk_read(clk) & ~(1 << clk->enable_bit), clk);
 	if (clk->status_reg) {
-		unsigned int (*read)(const void __iomem *addr);
+		unsigned int (*read)(void __iomem *addr);
 		int i;
 		void __iomem *mapped_status = (phys_addr_t)clk->status_reg -
 			(phys_addr_t)clk->enable_reg + clk->mapped_reg;
-- 
2.7.4

Re: [PATCH] sh: clk: Fix discarding const qualifier warning

[Geert Uytterhoeven]

Hi Krzysztof,

On Tue, Jan 7, 2020 at 1:26 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
> ioreadX() accepts pointer to non-const memory.  This fixes warnings
> like:
>
>     drivers/sh/clk/cpg.c: In function ‘r8’:
>     drivers/sh/clk/cpg.c:41:17: warning: passing argument 1 of ‘ioread8’
>         discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
>
> Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Thanks for your patch!

> --- a/drivers/sh/clk/cpg.c
> +++ b/drivers/sh/clk/cpg.c
> @@ -36,17 +36,17 @@ static void sh_clk_write(int value, struct clk *clk)
>                 iowrite32(value, clk->mapped_reg);
>  }
>
> -static unsigned int r8(const void __iomem *addr)
> +static unsigned int r8(void __iomem *addr)
>  {
>         return ioread8(addr);
>  }

Isn't the real issue that some implementations of ioreadX() take const,
while others don't?

Even the generic ones disagree:

    include/asm-generic/io.h:static inline u8 ioread8(const volatile
void __iomem *addr)
    include/asm-generic/iomap.h:extern unsigned int ioread8(void __iomem *);

IMHO they all should take "const volatile void __iomem *".

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] sh: clk: Fix discarding const qualifier warning

[Krzysztof Kozlowski]

On Tue, 7 Jan 2020 at 14:00, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Krzysztof,
>
> On Tue, Jan 7, 2020 at 1:26 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > ioreadX() accepts pointer to non-const memory.  This fixes warnings
> > like:
> >
> >     drivers/sh/clk/cpg.c: In function ‘r8’:
> >     drivers/sh/clk/cpg.c:41:17: warning: passing argument 1 of ‘ioread8’
> >         discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
> >
> > Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
>
> Thanks for your patch!
>
> > --- a/drivers/sh/clk/cpg.c
> > +++ b/drivers/sh/clk/cpg.c
> > @@ -36,17 +36,17 @@ static void sh_clk_write(int value, struct clk *clk)
> >                 iowrite32(value, clk->mapped_reg);
> >  }
> >
> > -static unsigned int r8(const void __iomem *addr)
> > +static unsigned int r8(void __iomem *addr)
> >  {
> >         return ioread8(addr);
> >  }
>
> Isn't the real issue that some implementations of ioreadX() take const,
> while others don't?
>
> Even the generic ones disagree:
>
>     include/asm-generic/io.h:static inline u8 ioread8(const volatile
> void __iomem *addr)
>     include/asm-generic/iomap.h:extern unsigned int ioread8(void __iomem *);
>
> IMHO they all should take "const volatile void __iomem *".

Since this is a SuperH driver, I adjusted it to the SuperH
implementation - lack of const. However iIndeed it makes sense to have
them all taking "const"... Let me check, if I can fix it (without the
real HW).

Best regards,
Krzysztof

Re: [PATCH] sh: clk: Fix discarding const qualifier warning

[Krzysztof Kozlowski]

On Tue, Jan 07, 2020 at 02:05:14PM +0100, Krzysztof Kozlowski wrote:
> On Tue, 7 Jan 2020 at 14:00, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >
> > Hi Krzysztof,
> >
> > On Tue, Jan 7, 2020 at 1:26 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > > ioreadX() accepts pointer to non-const memory.  This fixes warnings
> > > like:
> > >
> > >     drivers/sh/clk/cpg.c: In function ‘r8’:
> > >     drivers/sh/clk/cpg.c:41:17: warning: passing argument 1 of ‘ioread8’
> > >         discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
> > >
> > > Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> >
> > Thanks for your patch!
> >
> > > --- a/drivers/sh/clk/cpg.c
> > > +++ b/drivers/sh/clk/cpg.c
> > > @@ -36,17 +36,17 @@ static void sh_clk_write(int value, struct clk *clk)
> > >                 iowrite32(value, clk->mapped_reg);
> > >  }
> > >
> > > -static unsigned int r8(const void __iomem *addr)
> > > +static unsigned int r8(void __iomem *addr)
> > >  {
> > >         return ioread8(addr);
> > >  }
> >
> > Isn't the real issue that some implementations of ioreadX() take const,
> > while others don't?
> >
> > Even the generic ones disagree:
> >
> >     include/asm-generic/io.h:static inline u8 ioread8(const volatile
> > void __iomem *addr)
> >     include/asm-generic/iomap.h:extern unsigned int ioread8(void __iomem *);
> >
> > IMHO they all should take "const volatile void __iomem *".
> 
> Since this is a SuperH driver, I adjusted it to the SuperH
> implementation - lack of const. However iIndeed it makes sense to have
> them all taking "const"... Let me check, if I can fix it (without the
> real HW).

That will be non-trivial because many platforms define ioreadX() with
non-const. For example entire alpha with many its implementations of
ioread(). Even include/asm-generic/iomap.h defines them as non-const...

Best regards,
Krzysztof

Re: [PATCH] sh: clk: Fix discarding const qualifier warning

[Arnd Bergmann]

arch/powerpc/kernel/iomap.cOn Tue, Jan 7, 2020 at 2:33 PM Krzysztof
Kozlowski <krzk@kernel.org> wrote:
> On Tue, Jan 07, 2020 at 02:05:14PM +0100, Krzysztof Kozlowski wrote:
> > On Tue, 7 Jan 2020 at 14:00, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >
> > Since this is a SuperH driver, I adjusted it to the SuperH
> > implementation - lack of const. However iIndeed it makes sense to have
> > them all taking "const"... Let me check, if I can fix it (without the
> > real HW).
>
> That will be non-trivial because many platforms define ioreadX() with
> non-const. For example entire alpha with many its implementations of
> ioread(). Even include/asm-generic/iomap.h defines them as non-const...

I found these instances:

arch/alpha/include/asm/io.h
arch/alpha/kernel/io.c
arch/parisc/include/asm/io.h
arch/parisc/lib/iomap.c
arch/sh/kernel/iomap.c
arch/powerpc/kernel/iomap.c
lib/iomap.c
include/asm-generic/iomap.h

At least the last four file would have to be done at the same time as
the header is shared, but the actual conversion should be trivial.

       Arnd

Re: [PATCH] sh: clk: Fix discarding const qualifier warning

[Krzysztof Kozlowski]

On Tue, 7 Jan 2020 at 14:54, Arnd Bergmann <arnd@arndb.de> wrote:
>
> arch/powerpc/kernel/iomap.cOn Tue, Jan 7, 2020 at 2:33 PM Krzysztof
> Kozlowski <krzk@kernel.org> wrote:
> > On Tue, Jan 07, 2020 at 02:05:14PM +0100, Krzysztof Kozlowski wrote:
> > > On Tue, 7 Jan 2020 at 14:00, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > >
> > > Since this is a SuperH driver, I adjusted it to the SuperH
> > > implementation - lack of const. However iIndeed it makes sense to have
> > > them all taking "const"... Let me check, if I can fix it (without the
> > > real HW).
> >
> > That will be non-trivial because many platforms define ioreadX() with
> > non-const. For example entire alpha with many its implementations of
> > ioread(). Even include/asm-generic/iomap.h defines them as non-const...
>
> I found these instances:
>
> arch/alpha/include/asm/io.h
> arch/alpha/kernel/io.c
> arch/parisc/include/asm/io.h
> arch/parisc/lib/iomap.c
> arch/sh/kernel/iomap.c
> arch/powerpc/kernel/iomap.c
> lib/iomap.c
> include/asm-generic/iomap.h
>
> At least the last four file would have to be done at the same time as
> the header is shared, but the actual conversion should be trivial.

Yes, assuming that I did not screw up some specific
arch-implementation, it seems easy.

I have patchset ready - just need to build test it and I'll share for
kbuild & company to test.

Best regards,
Krzysztof