Re: [PATCH v6 1/5] Consolidate __memcpy_{to,from}io and __memset_io into iomap_copy.c

[Julian Vetter]

On 26.09.24 09:14, Arnd Bergmann wrote:
> On Wed, Sep 25, 2024, at 13:24, Julian Vetter wrote:
> > Various architectures have almost the same implementations for
> > __memcpy_{to,from}io and __memset_io functions. So, consolidate them
> > into the existing lib/iomap_copy.c.
> >
> > Reviewed-by: Yann Sionneau <ysionneau@xxxxxxxxxxxxx>
> > Signed-off-by: Julian Vetter <jvetter@xxxxxxxxxxxxx>
> > ---
> > Signed-off-by: Julian Vetter <jvetter@xxxxxxxxxxxxx>
>
> You have a duplicated signoff here.

Yes, thank you. I will remove it in the next patch revision.

> > +#ifndef __memcpy_fromio
> > +void __memcpy_fromio(void *to, const volatile void __iomem *from,
> > size_t count);
> > +#endif
> > +
> > +#ifndef __memcpy_toio
> > +void __memcpy_toio(volatile void __iomem *to, const void *from, size_t
> > count);
> > +#endif
> > +
> > +#ifndef __memset_io
> > +void __memset_io(volatile void __iomem *dst, int c, size_t count);
> > +#endif
>
> I'm not entirely sure about the purpose of the #ifdef here, since
> nothing ever overrides the double-underscore versions, both before
> and after your patches.
>
> Unless I'm missing something here, I think a more logical
> sequence would be:
>
> 1. add the definitions in this file without the underscores,

by: "...in this file..." you mean the 'lib/iomap_copy.c' file, right? 
But what if an architecture does not select 'CONFIG_HAS_IOMEM'. Then 
'iomap_copy.c' is not compiled and we don't have an implementation, 
right? I tried to compile with ARCH=um, with some MTD chip driver, like 
the robot did and it indeed fails, because um has 'NO_IOMEM' set. and 
the driver uses memcpy_fromio. I mean it's a strange combination, 
because apparently we try to use IO memory? Is this an invalid 
combination? But shouldn't the driver then 'depends on HAS_IOMEM'?

>     as memcpy_fromio/memcpy_toio/memset_io, with the #ifdef
>     for that name that is always set at this point
Right. I will remove it in my next patch revision.


> 2. replace the default implementation in asm-generic/io.h
>     with extern prototypes, remove the #define from those
Yes, I have done this now.

> 3. convert the other architectures, removing both the
>     implementations and the prototypes.

I have removed the prototypes and have aligned the function arguments in 
m68k, alpha, parisc, and sh, which all have their own implementation, 
but had slightly different function arguments. Btw, I have not removed 
their implementations because some of them seem to have optimized 
implementations (e.g., alpha and m68k), that I didn't want to touch. But 
you're right others (e.g., sh) just do byte wise accesses and have a 
comment "This needs to be optimized." Maybe I should remove these and 
let them use the new version?!

>       Arnd