dsp mmap change

Kostik Belousov kostikbel at gmail.com
Fri May 6 14:04:35 UTC 2011


On Fri, May 06, 2011 at 04:38:00PM +0300, Andriy Gapon wrote:
> on 06/05/2011 16:32 Kostik Belousov said the following:
> > On Fri, May 06, 2011 at 11:55:00AM +0300, Andriy Gapon wrote:
> >>
> >> I would like to ask for a review and/or testing of the following patch:
> >> http://people.freebsd.org/~avg/dev_dsp_mmap.diff
> >>
> >> It's supposed to fix an issue described here:
> >> http://lists.freebsd.org/pipermail/freebsd-multimedia/2011-February/011691.html
> >>
> >> In short, the following pseudo-code should do the right thing:
> >> fd = open(/dev/dsp, O_RDWR);
> >> mmap(PROT_READ, fd);
> >> mmap(PROT_WRITE, fd);
> >>
> >> Thank you!
> > 
> > I think that you have to call PCM_GIANT_LEAVE() when returning
> > EINVAL on the vm_pager_alloc() failure.
> 
> Yes, thank you.
> 
> > Your patch hardcodes an assumption that sndbufs are always
> > contiguous. I was unable to convince myself that this is true.
> 
> I think that this should be true for the case when DMA is used?
In the current driver, yes, but there is nothing that theoretically
prevents scatter-gather from be used.

> But, yes, very good point.

Updated patch looks fine (for me).
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