Messages in this thread | | | Subject | Re: [Alsa-devel] Re: [OT] ALSA userspace API complexity | From | Alan Cox <> | Date | Tue, 10 Jan 2006 00:44:58 +0000 |
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On Llu, 2006-01-09 at 16:29 -0800, David Lang wrote: > I was under the (apparently mistaken) impression that you couldn't DMA > from userspace (something to do with the possibility that the userspace > memory pages could be swapped out in the middle of the DMA)
Drivers can choose to support this two different ways. One is to have a buffer of kernel memory mapped into user space and shared with the hardware (this is how OSS did it), the other is to use the 2.6 get_user_pages API to get the physical address of a set of pages and lock them down so they don't wander off during DMA.
Both have advantages for different uses.
Alan
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