bus_dma (9). What exactly means "Loading of memory allocation" ?
Garrett Cooper
yanefbsd at gmail.com
Mon Feb 2 00:45:20 PST 2009
On Sun, Feb 1, 2009 at 5:56 PM, Sergey Babkin <babkin at 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 at 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
More information about the freebsd-hackers
mailing list