Re: [PATCH] New phys_addr() syscall

Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Mon, 20 Jul 1998 08:50:59 +1000

Alan Cox writes:
> > People writing pure userspace network drivers may also find this handy
> > if they want to DMA directly into userspace.
>
> It doesnt help. You have locking and copy/write issues to worry about for
> the DMA case. This seems an extremely fringe and bizarre syscall to consider
> for general use!

What issues? If I pin down a set of pages, I can then get their
physical address and tell the card to DMA its heart out. How exactly
is this going to fail?

I'm not claiming this syscall will be of general use: it is most
certainly specialised. However I don't see any argument for
restricting access.

BTW: I wrote this primarily for my memory tester.

Regards,

Richard....

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