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SubjectRe: can device drivers return non-ram via vm_ops->nopage?
On Sat, 20 Mar 2004, Russell King wrote:

> Actually, ALSA is broken in that respect - it isn't portable as it
> stands. It isn't the API which is broken - it's ALSA which is broken.
> Performing virt_to_page() on any non-direct mapped RAM page (which
> means the value returned from dma_alloc_coherent or pci_alloc_consistent)
> is undefined.
> One of my current projects is fixing this crap in ALSA.

Yes, but if there's no API in the kernel code allowing to obtain page
pointers using any value returned from dma_alloc_coherent(), then we
cannot fix this problem.

So, it's not much subsystem (ALSA) problem, but kernel core is not matured

The same problem is for the cache coherency for mmaped pages.


Jaroslav Kysela <>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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