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