Re: [PATCH 6/13] devres: implement managed iomap interface

[Kumar Gala]

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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