Date: Fri, 6 May 2011 16:16:40 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: multimedia@freebsd.org, current@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: dsp mmap change Message-ID: <201105061616.41145.jhb@freebsd.org> In-Reply-To: <20110506140428.GF48734@deviant.kiev.zoral.com.ua> References: <4DC3B764.4030801@FreeBSD.org> <4DC3F9B8.3030505@FreeBSD.org> <20110506140428.GF48734@deviant.kiev.zoral.com.ua>
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On Friday, May 06, 2011 10:04:28 am Kostik Belousov wrote: > 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. You could "fix" this by creating an sglist (via sglist_build()) and an OBJT_SG VM object that the d_mmap_single callback returned. I wish there was a cleaner way to just create a VM object and populate it with pages though, and then use vm_map_insert() to map it into the kernel rather than the more roundabout method of OBJT_SG. -- John Baldwin
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