Date: Wed, 29 Aug 2012 05:07:37 -0600 From: Scott Long <scott4long@yahoo.com> To: Adrian Chadd <adrian@freebsd.org> Cc: "scottl@freebsd.org" <scottl@freebsd.org>, "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org> Subject: Re: MIPS busdma map questions Message-ID: <77CDC9C5-A4DA-4CE6-ADEA-57DC6C9A2F0B@yahoo.com> In-Reply-To: <CAJ-VmonKM970eb3TvFkXh0CcjvRK8cF89L3f=MqNFw3nd-RWSQ@mail.gmail.com> References: <CAJ-VmomuwKKaQ6AszeDo-iQwL%2B8DPJpBB9av0K%2BVbaj2feHO7g@mail.gmail.com> <1F780BF4-84C3-48D5-9832-EA32381969A6@bsdimp.com> <CAJ-VmokHX7=Jd06tJWmAJfTGtuF4WfgpgGb0f0PwUzfP-QpJ0Q@mail.gmail.com> <08166FD3-8FAD-453D-ABD3-2DC19B52FED1@yahoo.com> <CAJ-VmonKM970eb3TvFkXh0CcjvRK8cF89L3f=MqNFw3nd-RWSQ@mail.gmail.com>
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On Aug 29, 2012, at 3:21 AM, Adrian Chadd <adrian@freebsd.org> wrote: > On 28 August 2012 22:01, Scott Long <scott4long@yahoo.com> wrote: >=20 >> There is no need to create a separate map for memory allocated via this w= ay. It's a convenience thing. >=20 > Right, but my initial question still stands - the initial map that's > being created is completely ignored and overwritten when the > bus_dmamem_alloc() call is made. One of the first thing that does is > it sets *dmat =3D NULL; - it's totally trashing the pre-existing map. >=20 >=20 Right. You don't create a separate map for this kind of allocation, you let= bus_dmamem_alloc do that for you. The inputs to this function are the tag a= nd the flags. The output is the map and the vaddr for the allocation. The m= ap argument is an output, not an input. Does that make more sense? Scott=
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