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SubjectRe: mm question


On Mon, 10 Dec 2001, Alan Cox wrote:

> > How does one do the following task: obtain a bunch of free pages (around
> > 300K) with physical addresses between certain bounds (more then
> > 0x4000000, but it is likely this is not constant) reserver them and map to
> > kernel space so that the driver can access them directly ?
>
> We support allocating pages below 16Mb, below 4Gb, or anywhere within RAM
> on x86. If you want to within a range or your 300K must be a single 300K
> block then you need to allocate it at boot time
>

It does not have to be contiguous. I was thinking of simply starting with
the smallest address and trying to free the pages until the needed amount
is available. But I have no idea how to properly do locking or force the
page to be swapped out or something.

As for doing this during boot time this does not seem like a good idea for
two reasons:
a) I need at least _two_ buffers 300K each
b) the actual amount of RAM needed changes depending on video standard
(this is for video capture).

thanks

Vladimir Dergachev

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