RE: Alloc and lock down large amounts of memory

From: Bhavana Nagendra (
Date: Tue Aug 20 2002 - 15:08:23 EST

> Curiosity: why do you want to do device DMA buffer
> allocation from userland?

I need 256M memory for a graphics operation. It's a requiremment,
can't change it. There will be other reasonably sized allocs in kernel
space, this is a special case that will be done from userland. As
discussed earlier in this thread, there's no good way of alloc()ing
and pinning that much in DMA memory space, is there?

Gilad, I looked at mm/memory.c and map_user_kiobuf() lets me
map user memory into kernel memory and pins it down. A scatter
gatter mapping (say, pci_map_sg()) will create a seemingly
contiguous buffer for DMA purposes. Does that sound right to you?

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