bus_dma (9). What exactly means "Loading of memory allocation" ?

[Garrett Cooper]

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