Date: Mon, 2 Feb 2009 00:46:07 -0800 From: Garrett Cooper <yanefbsd@gmail.com> To: Sergey Babkin <babkin@verizon.net> Cc: bsd.quest@googlemail.com, freebsd-hackers@freebsd.org Subject: Re: bus_dma (9). What exactly means "Loading of memory allocation" ? Message-ID: <7d6fde3d0902020046o7640f217ye88336b53920a538@mail.gmail.com> In-Reply-To: <7d6fde3d0902020045h55255cane0d6dd9f64d23f5@mail.gmail.com> References: <6699015.16785.1233539817447.JavaMail.root@vms063.mailsrvcs.net> <7d6fde3d0902020045h55255cane0d6dd9f64d23f5@mail.gmail.com>
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On Mon, Feb 2, 2009 at 12:45 AM, Garrett Cooper <yanefbsd@gmail.com> wrote: > On Sun, Feb 1, 2009 at 5:56 PM, Sergey Babkin <babkin@verizon.net> wrote: >> >> If I remember correctly, loading means that the pages become mapped >> and visible to the devices. Some buses can access only a limited >> address space , like ISA has only a 24-bit address. When a map gets >> loaded, for any pages outside of this range the temporary in-ramge >> pages are allocated and the d ata gets moved through them. On some >> machines, like I think DEC Alpha, the physicall addresses seen by >> the devices are not the same as seen by the CPU , these need to be >> translated. And so on. >> I think my real old articl e had some of these explanations but now >> the Daemonnews site seems to be re al slow: >> http://ezine.daemonnews.org/200008/isa.html >> -SB >> (sorry a bout top quoting, it's the only kind the web interface of my >> provider suppo rts) >> Feb 1, 2009 03:38:27 PM, [1]bsd.quest@googlemail.com wrote: >> >> Hi, >> at first the cut of text from man (9) bus_dma: >> bus_dmamap_t >> A machine-dependent opaque type describing an individual >> mapp ing. >> One map is used for each memory allocation that will b e loaded. >> Maps can be reused once they have been unloaded.. . >> Question: What exactly means "Loading of memory allocation" in thi s context >> ? >> Could anyone explain it or give me some little example wi th DMA >> functions >> for understanding it. > > Unfortunately it's bad English, so that might be where some of the > confusion is stemming from. I'll send a doc's PR request after this to > fix it. > -Garrett Ugh. Nevermind. The question was written improperly -- the manpage wasn't ><. -Garrett
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