Date: Tue, 28 Aug 2012 23:01:02 -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: <08166FD3-8FAD-453D-ABD3-2DC19B52FED1@yahoo.com> In-Reply-To: <CAJ-VmokHX7=Jd06tJWmAJfTGtuF4WfgpgGb0f0PwUzfP-QpJ0Q@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>
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On Aug 28, 2012, at 9:43 PM, Adrian Chadd <adrian@freebsd.org> wrote: > On 28 August 2012 20:24, Warner Losh <imp@bsdimp.com> wrote: >> >> On Aug 28, 2012, at 8:22 PM, Adrian Chadd wrote: >> >>> Hi, >>> >>> I have a couple of busdma map questions. >>> >>> #1 - in mips/mips/busdma_machdep.c, bus_dmamap_destroy() calls >>> _busdma_free_dmamap() and -then- goes and walks the dma map list. Is >>> this a good idea or not? :) >> >> Accessing free memory after freeing it is a free ticket to a free dose of free pain. It should be freed after the if that checks to see if it is in use. > > Excellent! Who knows busdma better than I and can wade through what > that code path is doing? :) > > > There is no need to create a separate map for memory allocated via this way. It's a convenience thing. Scotthelp
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