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SubjectRe: mmap
Date wrote:
> I am doing the following:
> malloc some memory is user space
> pass its pointer to some kernel module
> in the kernel a pci_alloc_consistent so that i get a memory
> region for PCI DMA operations

Wrong approach, you can use kiobufs if you want DMA to the malloc()ed
userspace memory:

* lock down the user memory using map_user_kiobuf() + lock_kiovec()
(see linux/iobuf.h).
* translate the iobuf->maplist into a scatterlist [1]
* feed pci_map_sg() with the scatterlist to get DMA addresses.
you can pass to the hardware.

And the reverse to free everything when you are done of course.


[1] IMHO it would be more useful if iobufs would use a scatterlist
instead of an struct page* array.

Gerd Knorr <> -- SuSE Labs, Außenstelle Berlin
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