Re: Question about ioremap and io_remap_page_range

Jonathan Lundell (
Thu, 27 Sep 2001 10:42:15 -0700

At 8:33 AM -0600 2001-09-27, Jonathan Corbet wrote:
> > > VIRT_ADDR = ioremap(BUS_ADDR); to map a section of PCI memory, and
>> > X_ADDR = virt_to_phys(VIRT_ADDR);
>> i'd suggest to read Documentation/DMA-mapping.txt in any recent kernel
>> source, the bus_to_virt()/virt_to_phys() interface is obsolete and has
>> been replaced by the pci_alloc_*/pci_map_*/pci_free_*() dynamic
>> DMA-mapping API.
>...or, of course, _Linux_Device_Drivers_, Second Edition, available online
>at The DMA chapter covers
>this API as well.

That chapter says, in small part,

>Based on this discussion, you might also want to map addresses
>returned by ioremap to user space. This mapping is easily
>accomplished because you can use remap_page_range directly, without
>implementing methods for virtual memory areas. In other words,
>remap_page_range is already usable for building new page tables that
>map I/O memory to user space

Are you suggesting that ioremap() objects can be passed to
remap_page_range()? How can that be valid?

Also, there's an html conversion error:

> if (offset >= _ _pa(high_memory) || (filp->f_flags & O_SYNC))

Looks like   got translated to  

/Jonathan Lundell.
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