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Re: pci_alloc_consistent usage

To: Christoph Hellwig <hch@infradead.org>
Subject: Re: pci_alloc_consistent usage
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 27 May 2003 13:45:51 +0200
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>, wgowcher@yahoo.com, linux-mips@linux-mips.org
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On Tue, May 27, 2003 at 12:33:29PM +0100, Christoph Hellwig wrote:

> On Tue, May 27, 2003 at 01:22:37PM +0200, Ralf Baechle wrote:
> > [...]
> > portably refer to any piece of memory.  If you have a cpu pointer
> > (which may be validly DMA'd too) you may easily obtain the page
> > and offset using something like this:
> >                                                                             
> >     
> >         struct page *page = virt_to_page(ptr);
> >         unsigned long offset = ((unsigned long)ptr & ~PAGE_MASK);
> > [...]
> > 
> > While it's officially documented I still don't like it.
> 
> Hmm, I remembered that some ports used vmalloc-like allocators for
> this and virt_to_page doesn't work for those..

There's at least one MIPS system which we don't support anymore but which
would have to be supported by something like this.

Whatever - virt_to_page should then be considered a a legacy API which we
have to try to support as well as possible in the hope it's going to fade
away ...

  Ralf

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