linux-kernel - Re: [PATCH 1/3] video: fbdev: vt8623fb: suppress build warning

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Date:	Thu, 4 Dec 2014 15:40:51 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Prabhakar Lad <prabhakar.csengg@...il.com>
CC:	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	LFBDEV <linux-fbdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] video: fbdev: vt8623fb: suppress build warning

On 04/12/14 15:29, Geert Uytterhoeven wrote:
> On Thu, Dec 4, 2014 at 8:56 AM, Tomi Valkeinen <tomi.valkeinen@...com> wrote:
>> On 04/12/14 09:46, Sudip Mukherjee wrote:
>>> On Thu, Dec 04, 2014 at 09:05:46AM +0200, Tomi Valkeinen wrote:
>>>> On 03/12/14 20:29, Prabhakar Lad wrote:
>>>>> On Wed, Dec 3, 2014 at 11:49 AM, Tomi Valkeinen <tomi.valkeinen@...com> wrote:
>>>>>> On 27/11/14 00:07, Lad, Prabhakar wrote:
>>>>>>> this patch fixes following build warning:
>>>>>>> drivers/video/fbdev/vt8623fb.c: In function ‘vt8623_pci_probe’:
>>>>>>> drivers/video/fbdev/vt8623fb.c:734:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
>>>>>>>   par->state.vgabase = (void __iomem *) vga_res.start;
>>>>>>>                        ^
>>>>>>> Signed-off-by: Lad, Prabhakar <prabhakar.csengg@...il.com>
>>>>>>> ---
>>>>>>>  drivers/video/fbdev/vt8623fb.c | 2 +-
>>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/drivers/video/fbdev/vt8623fb.c b/drivers/video/fbdev/vt8623fb.c
>>>>>>> index 5c7cbc6..ea7f056 100644
>>>>>>> --- a/drivers/video/fbdev/vt8623fb.c
>>>>>>> +++ b/drivers/video/fbdev/vt8623fb.c
>>>>>>> @@ -731,7 +731,7 @@ static int vt8623_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
>>>>>>>
>>>>>>>       pcibios_bus_to_resource(dev->bus, &vga_res, &bus_reg);
>>>>>>>
>>>>>>> -     par->state.vgabase = (void __iomem *) vga_res.start;
>>>>>>> +     par->state.vgabase = (void __iomem *) (unsigned long) vga_res.start;
>>>>>>
>>>>>> This does look quite ugly... Where does the warning come from in the
>>>>>> first place. Isn't vga_res.start (resource_size_t) the size of a pointer?
>>>>>>
>>>>> Yes looks ugly, I am not sure what you meant from 'where does this warning
>>>>> come from' its in the commit message.
>>>>
>>>> I meant why is there a warning at all. With a quick glance,
>>>> vga_res.start is the size of a pointer. So the sizes of the integer and
>>>> the pointer should be the same. But the warning still says "of different
>>>> size".
>>>
>>> poking my nose into your discussion.
>>> I tried to see the warning, and I re-compiled like make W=1 M=drivers/video/fbdev/ (before that make clean M=drivers/video/fbdev was done)
>>> I can see warning with many other files, but drivers/video/fbdev/vt8623fb.o was quiet and there was no warning.
>>> I tested with next=20141203.
>>> did i miss something in checking the warning ?
>>
>> I don't see the warning either when compiling for arm or x86_64. On what
>> architecture do you see the warning?
> 
> On 32-bit systems with PHYS_ADDR_T_64BIT=y, resource_size_t is u64,
> while pointers are still 32-bit.

Ah, I see. Yes, I can reproduce the warning with that config.

So, still rather ugly, but looks correct to me, so I'll apply the series.

 Tomi



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