Alan Cox wrote:
On Maw, 2006-04-18 at 04:18 +1000, Nick Piggin wrote:
I'm pretty sure you can't remap_pfn_range vmalloced memory because
it doesn't use contiguous page frames.
To remap vmalloc memory you need something like this. Note that vmalloc
memory may not be DMA accessible, vmalloc_32 memory maybe. Alternatively
you can build your own scatter gather lists from pages subject to
hardware limits.
The following GPL code from various drivers shows how to do vmalloc
mapping into an application. Having a common helper for this is a
discussion/todo item when that area of the vm gets future adjustments
but for now this code should do the trick:
Yep, that would be a good option, thanks Alan.
You can look through the tree at how drivers remap their rvmalloced
memory -- (here's a snippet from drivers/media/video/meye.c):
while (size > 0) {
page = vmalloc_to_pfn((void *)pos);
if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
mutex_unlock(&meye.lock);
return -EAGAIN;
}
start += PAGE_SIZE;
pos += PAGE_SIZE;
if (size > PAGE_SIZE)
size -= PAGE_SIZE;
else
size = 0;
}
The trick is to get the underlying pfns and remap one at a time.
You could also tinker with vmalloc_to_page+vm_insert_page, although
that might not yet be the best option for an out of tree driver.
--
SUSE Labs, Novell Inc.
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