Scatter Gather question : 2.6.test4 . page to vaddr

Scatter Gather question : 2.6.test4 . page to vaddr

[jd]

Hi,

I see that 2.6 scatterlist.h has eliminated the "address" element
and uses page struct only, and that  pci_map_sg() is used to 
populate the dma_address field. I'm not really planning on
using DMA .

How can I convert the page * entry 
pointed to by  SCpnt->request_buffer   back to a vaddr ? 
I don't see a page-to-vaddr() . function ?
Thanks for any insight.

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Re: Scatter Gather question : 2.6.test4 . page to vaddr

[jd]

--- jd <jpd_hp_linux_scsi@yahoo.com> wrote:
> 
> Hi,
> 
> I see that 2.6 scatterlist.h has eliminated the "address" element
> and uses page struct only, and that  pci_map_sg() is used to 
> populate the dma_address field. I'm not really planning on
> using DMA .
> 
> How can I convert the page * entry 
> pointed to by  SCpnt->request_buffer   back to a vaddr ? 
> I don't see a page-to-vaddr() . function ?
> Thanks for any insight.
> 
   Looks like 
  cur_ptr = (void *) pfn_to_kaddr( page_to_pfn(sg->page));

 Did it  ( At least once ;) )  !



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Re: Scatter Gather question : 2.6.test4 . page to vaddr

[James Bottomley]

On Mon, 2003-09-22 at 15:15, jd wrote:
> I see that 2.6 scatterlist.h has eliminated the "address" element
> and uses page struct only, and that  pci_map_sg() is used to 
> populate the dma_address field. I'm not really planning on
> using DMA .
> 
> How can I convert the page * entry 
> pointed to by  SCpnt->request_buffer   back to a vaddr ? 
> I don't see a page-to-vaddr() . function ?
> Thanks for any insight.

In general, you can't...the page may not be mapped in the kernel's
space.  You can use kmap/kunmap to look at its contents.

James

Re: Scatter Gather question : 2.6.test4 . page to vaddr

[Matthew Wilcox]

On Mon, Sep 22, 2003 at 01:15:40PM -0700, jd wrote:
> I see that 2.6 scatterlist.h has eliminated the "address" element
> and uses page struct only, and that  pci_map_sg() is used to 
> populate the dma_address field. I'm not really planning on
> using DMA .
> 
> How can I convert the page * entry 
> pointed to by  SCpnt->request_buffer   back to a vaddr ? 
> I don't see a page-to-vaddr() . function ?

The trick is that there may not be a vaddr for that struct page.  If it's
in highmem on x86, then it only ever gets temporary mappings into the
kernel's space.  You're probably looking for kmap(), kmap_atomic() or,
if you really really know it's a lowmem page, page_address().

-- 
"It's not Hollywood.  War is real, war is primarily not about defeat or
victory, it is about death.  I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk