Re: [PATCH v6 5/6] fbdev: Move framebuffer I/O helpers into <asm/fb.h>

[Thomas Zimmermann]

Hi

Am 10.05.23 um 16:15 schrieb Arnd Bergmann:
> On Wed, May 10, 2023, at 16:03, kernel test robot wrote:
>
> >     cc1: warning: arch/sh/include/mach-hp6xx: No such file or directory
> > [-Wmissing-include-dirs]
> >     cc1: warning: arch/sh/include/mach-hp6xx: No such file or directory
> > [-Wmissing-include-dirs]
> >     In file included from drivers/video/fbdev/hitfb.c:27:
> >     drivers/video/fbdev/hitfb.c: In function 'hitfb_accel_wait':
> > > > arch/sh/include/asm/hd64461.h:18:33: warning: passing argument 1 of 'fb_readw' makes pointer from integer without a cast [-Wint-conversion]
> >        18 | #define HD64461_IO_OFFSET(x)    (HD64461_IOBASE + (x))
> >           |                                 ^~~~~~~~~~~~~~~~~~~~~~
> >           |                                 |
> >           |                                 unsigned int
> >     arch/sh/include/asm/hd64461.h:93:33: note: in expansion of macro
> > 'HD64461_IO_OFFSET'
> >        93 | #define HD64461_GRCFGR          HD64461_IO_OFFSET(0x1044)
> >     /* Accelerator Configuration Register */
> >           |                                 ^~~~~~~~~~~~~~~~~
> >     drivers/video/fbdev/hitfb.c:47:25: note: in expansion of macro
> > 'HD64461_GRCFGR'
> >        47 |         while (fb_readw(HD64461_GRCFGR) &
> > HD64461_GRCFGR_ACCSTATUS) ;
>
> I think that's a preexisting bug and I have no idea what the
> correct solution is. Looking for HD64461 shows it being used
> both with inw/outw and readw/writew, so there is no way to have
> the correct type. The sh __raw_readw() definition hides this bug,
> but that is a problem with arch/sh and it probably hides others
> as well.

The constant HD64461_IOBASE is defined as integer at


https://elixir.bootlin.com/linux/latest/source/arch/sh/include/asm/hd64461.h#L17

but fb_readw() expects a volatile-void pointer. I guess we could add a 
cast somewhere to silence the problem. In the current upstream code, 
that appears to be done by sh's __raw_readw() internally:


https://elixir.bootlin.com/linux/latest/source/arch/sh/include/asm/io.h#L35

Best regards
Thomas

>         Arnd

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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