linux-kernel - Re: [PATCH] fbdev: suppress warning when assigning vga-save/restore base

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Date:	Mon, 10 Feb 2014 12:32:28 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>
Cc:	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Ondrej Zajicek <santiago@...reenet.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] fbdev: suppress warning when assigning vga-save/restore base

Hi Tomi

On Mon, Feb 10, 2014 at 12:23 PM, Tomi Valkeinen <tomi.valkeinen@...com> wrote:
> Hi David,
>
> On 04/08/13 20:25, David Herrmann wrote:
>> If drivers use "struct resource" objects to retrieve the vga-base, they
>> must correctly cast the integer to pointer. With x86+PAE we have 32bit
>> pointers but 64bit resource_size_t. Hence, cast it to "unsigned long"
>> before casting to "void*" to suppress warnings due to size differences.
>>
>> As IO addresses are always low addresses, we can safely drop the higher
>> part of the address. This is what these drivers did before, anyway.
>>
>> Signed-off-by: David Herrmann <dh.herrmann@...il.com>
>> Reported-by: H. Peter Anvin <hpa@...or.com>
>> ---
>> Hi
>>
>> hpa reported build-warnings on i386+PAE:
>> /home/hpa/kernel/distwork/drivers/video/arkfb.c:1019:23: warning: cast to
>>     pointer from integer of different size [-Wint-to-pointer-cast]
>>     par->state.vgabase = (void __iomem *) vga_res.start;
>>                          ^
>> /home/hpa/kernel/distwork/drivers/video/s3fb.c: In function 's3_pci_probe':
>> /home/hpa/kernel/distwork/drivers/video/s3fb.c:1186:23: warning: cast to pointer
>>     from integer of different size [-Wint-to-pointer-cast]
>>     par->state.vgabase = (void __iomem *) vga_res.start;
>>                          ^
>>
>> This is due to resource_size_t being 64bit but "void*" 32bit. This patch tries
>> to suppress these warnings but I am not really comfortable fixing this. I have
>> no idea whether my assumption (IO address are 32bit) is right. Please verify.
>>
>>  @David: The following 3 commits of yours presumably introduced the warnings. I
>> would be glad if you could review this:
>
> What was the conclusion on this patch? Should I apply for 3.14 fixes?

No, please drop it. If I understand David correctly, we should just
revert the patches in question. But someone who actually understands
what it is doing should propose that (which is not me..).

Thanks
David
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