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

Thomas Zimmermann <tzimmermann@xxxxxxx> · Wed, 10 May 2023 16:27:10 +0200

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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