|| ||Russell King <rmk+lkml-AT-arm.linux.org.uk>|
|| ||Takashi Iwai <tiwai-AT-suse.de>|
|| ||Re: DMA API issues|
|| ||Wed, 23 Jun 2004 13:34:23 +0100|
|| ||Linus Torvalds <torvalds-AT-osdl.org>,
Jeff Garzik <jgarzik-AT-pobox.com>,
Matt Porter <mporter-AT-kernel.crashing.org>,
Jamey Hicks <jamey.hicks-AT-hp.com>, Ian Molton <spyro-AT-f2s.com>,
linux-kernel-AT-vger.kernel.org, greg-AT-kroah.com, tony-AT-atomide.com,
On Tue, Jun 22, 2004 at 12:40:45PM +0200, Takashi Iwai wrote:
> At Mon, 21 Jun 2004 20:26:39 -0700 (PDT),
> Linus Torvalds wrote:
> > On Mon, 21 Jun 2004, Linus Torvalds wrote:
> > >
> > > The argument at some point was that some architectures may not even _have_
> > > a "struct page" for DMA memory, since it's not "normal" memory (ie "slow
> > > memory" on m68k). However, I thought we all agreed that such a "struct
> > > page" could be furnished if that architecture wants so support mmap'ing.
> > .. which is not to say that we shouldn't have a "pci_mmap_pages()" thing
> > _too_. Pretty clearly the easiest interface often is to just map the pages
> > at mmap() time, and then we should just have a helper function to do that.
> > I thought we did one already, but hey, maybe not.
> I don't think we have such.
> Russell has once proposed a similar one (but not pci-specific), and I
> believe it makes sense for many drivers. We can hide the
> architecture-specific cache handling inside the helper function, too.
Ok. So does anyone have any objections if I push the ARM DMA mmap
interface upstream, which consists of:
* dma_mmap_coherent - map a coherent DMA allocation into user space
* @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
* @vma: vm_area_struct describing requested user mapping
* @cpu_addr: kernel CPU-view address returned from dma_alloc_coherent
* @handle: device-view address returned from dma_alloc_coherent
* @size: size of memory originally requested in dma_alloc_coherent
* Map a coherent DMA buffer previously allocated by dma_alloc_coherent
* into user space. The coherent DMA buffer must not be freed by the
* driver until the user space mapping has been released.
int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t handle, size_t size);
and a similar one for the ARM-specific "write combining" case (for
framebuffers utilising the DMA API)?
This was discussed on linux-arch, and the discussion died while trying
to settle on a suitable interface through apparant lack of interest.
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to firstname.lastname@example.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
to post comments)