[PATCH 6/13] devres: implement managed iomap interface
Kumar Gala
galak at kernel.crashing.org
Fri Apr 11 05:40:52 EST 2008
On Apr 10, 2008, at 1:24 PM, Sergei Shtylyov wrote:
> Kumar Gala wrote:
>
>>>>>> Those functions are going to break on 32-bit platforms with
>>>>>> extended physical address (well, that's starting with Pentiums
>>>>>> which had 36-bit PAE :-) AND devices mapped beyond 4 GB (e.g.
>>>>>> PowerPC 44x). You should have used resource_size_t for the
>>>>>> 'offset' parameter. As this most probably means that libata is
>>>>>> broken on such platforms, I'm going to submit a patch...
>
>>>> It's broken with drivers using MMIO, I meant to say.
>
>>> Oops, I meant PCI drivers here, at least for the time being. And
>>> it looks like that was a false alarm. :-]
>
>>>>> Yeah, right please go ahead. But I wonder whether any BIOS was
>>>>> actually crazy enough to map mmio region above 4G on 32bit
>>>>> machine.
>
>>>> This is a *hardware* mapping on some non-x86 platforms (like
>>>> PPC 44x or MIPS Alchemy). The arch/ppc/ and arch/mips/ kernels
>>>> have special hooks called from ioremap() which help create an
>>>> illusion that the PCI memory space on such platforms (not only
>>>> it) is mapped below 4 GB; arch/powerpc/ kernel doesn't do this
>>>> anymore -- hence this newly encountered issue.
>
>>> I thought that pcim_iomap() used devm_ioremap() or something --
>>> which of course turned to be wrong. devm_ioremap() alone is yet
>>> safe since there are no users for it amongst PPC 44x platform
>>> device drivers...
>
>> but there is no reason not to make it work properly. For example
>> I believe libata uses devm_* and the fsl SATA driver (non-PCI)
>> will need to work in cases similar to the 44x.
>
> Well, as for sata_fsl, it calls of_iomap() which does The Right
> Thing.
Fair, but I don't see why we should introduce new APIs that are
already "broken". We went through a lot of effort to clean up and
introduce resource_t (and clearly still have some bugs) for the >32-
bit physical address problem.
- k
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