Date: Mon, 14 Aug 2000 13:59:13 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: Bill Clinton <biffey@hotmail.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: dma to userland address Message-ID: <Pine.BSF.4.10.10008141359020.13324-100000@beppo.feral.com> In-Reply-To: <F89TuHZncJfKHmj9n1x00001510@hotmail.com>
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Look at what physio does.
On Mon, 14 Aug 2000, Bill Clinton wrote:
> lets say, hypothetically, that i have an ioctl interface to my device
> driver that takes a buffer that looks something like:
>
> struct {
> int length;
> char *buf;
> } mystruct;
>
> and lets say, hypothetically, that i wanted to dma directly
> to/from 'buf'. how would i do that?
>
> i've tried doing vtophys on buf, but that doesn't seem to work.
>
> i've tried doing vtophys on a kernel-allocated block and the mmapping it
> through /dev/mem in userland, but that doesn't seem to work either (this
> may have a bug, though - it worked under linux, but was about 10x slower
> than just leaving the kernel/user copy in there).
>
> so what am i missing here?
>
> - j
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