Re: can device drivers return non-ram via vm_ops->nopage?

[Jaroslav Kysela]

On Sat, 20 Mar 2004, Russell King wrote:

> It is well known that virt_to_page() is only valid on virtual addresses
> which correspond to kernel direct mapped RAM pages, and undefined on
> everything else.  Unfortunately, ALSA has been using it with
> pci_alloc_consistent() for a long time, and this behaviour is what
> makes ALSA broken.  The fact it works on x86 is merely incidental.

It works on PPC as well (at least we have no error reports).

> If ALSA wants this functionality, the ALSA people should ideally have
> put their requirements forward during the 2.5 development cycle so the
> problem could be addressed.

Yes, I'm sorry about that, but the ->nopage usage was requested by Jeff
Garzik and we're not gurus for the VM stuff. Because we're probably first
starting using of this mapping scheme, it resulted to problems.

> However, luckily in this instance, it is not a big problem to solve.  
> It just requires time to sort through all the abstraction layers upon
> abstraction layers which ALSA has.
> 
> - and I'm doing exactly this, right now.  Be patient. -

Thanks a lot.

						Jaroslav

-----
Jaroslav Kysela <perex@xxxxxxx>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/