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: > >> There is no need to create a separate map for memory allocated via this way. It's a convenience thing. > > 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 = NULL; - it's totally trashing the pre-existing map. > > 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 and the flags. The output is the map and the vaddr for the allocation. The map argument is an output, not an input. Does that make more sense? Scott
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