Date: Sat, 7 May 2011 22:16:25 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: multimedia@freebsd.org, freebsd-current@freebsd.org, current@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: dsp mmap change Message-ID: <20110507191625.GQ48734@deviant.kiev.zoral.com.ua> In-Reply-To: <201105061616.41145.jhb@freebsd.org> References: <4DC3B764.4030801@FreeBSD.org> <4DC3F9B8.3030505@FreeBSD.org> <20110506140428.GF48734@deviant.kiev.zoral.com.ua> <201105061616.41145.jhb@freebsd.org>
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--HevQWRStXZ0Cpw2M Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, May 06, 2011 at 04:16:40PM -0400, John Baldwin wrote: > 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 p= atch: > > > >> 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 =3D open(/dev/dsp, O_RDWR); > > > >> mmap(PROT_READ, fd); > > > >> mmap(PROT_WRITE, fd); > > > >> > > > >> Thank you! > > > >=20 > > > > I think that you have to call PCM_GIANT_LEAVE() when returning > > > > EINVAL on the vm_pager_alloc() failure. > > >=20 > > > Yes, thank you. > > >=20 > > > > Your patch hardcodes an assumption that sndbufs are always > > > > contiguous. I was unable to convince myself that this is true. > > >=20 > > > 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. >=20 > 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. You cannot have one page inserted into two vm objects. Contigmalloc() inserts the allocated pages into kernel_object. --HevQWRStXZ0Cpw2M Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk3FmokACgkQC3+MBN1Mb4iDLwCgps2E+M4fO+/UnaXayuKxu/z5 WbkAn3TzyN2mZ0VfdXxLQuCfM0ozqtbo =xWwZ -----END PGP SIGNATURE----- --HevQWRStXZ0Cpw2M--
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