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SubjectRe: mmap
I use the 'map_user_kiobuf' and 'lock_kiovec' kernel routines in a module
for 'user space memory'. After that if I pass the
'(iobuf->maplist[0])-mem_map) << PAGE_SHIFT)' to the hardware for DMA
operations and it works fine for Intel platforms. Now how can I use the
'iobuf' struct obtained after lock_kiovec operation to get a PCI bus
address that I can pass to hardware for DMA operations on my Apple
machine.?

thanks,
Daljeet.


|--------+----------------------->
| | Gerd Knorr |
| | <kraxel@bytes|
| | ex.org> |
| | |
| | 05/15/01 |
| | 01:03 PM |
| | Please |
| | respond to |
| | Gerd Knorr |
| | |
|--------+----------------------->
>-----------------------------------------------------------------------|
| |
| To: linux-kernel@vger.kernel.org |
| cc: (bcc: Daljeet Maini/India/IBM) |
| Subject: Re: mmap |
>-----------------------------------------------------------------------|






mdaljeet@in.ibm.com wrote:
> I am doing the following:
>
> malloc some memory is user space
> pass its pointer to some kernel module
> in the kernel module...do 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.

Gerd

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


--
Gerd Knorr <kraxel@bytesex.org> -- SuSE Labs, Außenstelle Berlin
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