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

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Arnd Bergmann <arnd@arndb.de>, kernel test robot <lkp@intel.com>,
	Helge Deller <deller@gmx.de>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Javier Martinez Canillas <javierm@redhat.com>,
	Daniel Vetter <daniel@ffwll.ch>, Vineet Gupta <vgupta@kernel.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	"David S . Miller" <davem@davemloft.net>,
	"James E . J . Bottomley" <James.Bottomley@hansenpartnership.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	suijingfeng@loongson.cn
Cc: oe-kbuild-all@lists.linux.dev,
	Linux-Arch <linux-arch@vger.kernel.org>,
	linux-fbdev@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org, linux-m68k@lists.linux-m68k.org,
	loongarch@lists.linux.dev, sparclinux@vger.kernel.org,
	linux-snps-arc@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v6 5/6] fbdev: Move framebuffer I/O helpers into <asm/fb.h>
Date: Wed, 10 May 2023 16:27:10 +0200	[thread overview]
Message-ID: <49684d58-c19d-b147-5e9f-2ac526dd50f0@suse.de> (raw)
In-Reply-To: <f6b2d541-d235-4e98-afcc-9137fb8afa35@app.fastmail.com>

[-- Attachment #1.1.1: Type: text/plain, Size: 2376 bytes --]

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)

[-- Attachment #1.2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 840 bytes --]

[-- Attachment #2: Type: text/plain, Size: 170 bytes --]

_______________________________________________
linux-snps-arc mailing list
linux-snps-arc@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-snps-arc