Date: Mon, 2 Feb 2009 00:45:15 -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: <7d6fde3d0902020045h55255cane0d6dd9f64d23f5@mail.gmail.com> In-Reply-To: <6699015.16785.1233539817447.JavaMail.root@vms063.mailsrvcs.net> References: <6699015.16785.1233539817447.JavaMail.root@vms063.mailsrvcs.net>
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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
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