<s>
In	O
computing	O
,	O
busdma	O
,	O
bus_dma	O
and	O
bus_space	O
is	O
a	O
set	O
of	O
application	B-Application
programming	I-Application
interfaces	I-Application
designed	O
to	O
help	O
make	O
device	B-Application
drivers	I-Application
less	O
dependent	O
on	O
platform-specific	O
code	O
,	O
thereby	O
allowing	O
the	O
host	O
operating	B-General_Concept
system	I-General_Concept
to	O
be	O
more	O
easily	O
ported	B-Architecture
to	O
new	O
computer	O
hardware	O
.	O
</s>
<s>
This	O
is	O
accomplished	O
by	O
having	O
abstractions	O
for	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
mapping	O
across	O
popular	O
machine-independent	O
computer	B-General_Concept
buses	I-General_Concept
like	O
PCI	B-Protocol
,	O
which	O
are	O
used	O
on	O
distinct	O
architectures	O
from	O
IA-32	B-Device
(	O
NetBSD/i386	O
)	O
to	O
DEC	B-Device
Alpha	I-Device
(	O
NetBSD/alpha	O
)	O
.	O
</s>
<s>
Additionally	O
,	O
some	O
devices	O
may	O
come	O
in	O
multiple	O
flavours	O
supporting	O
more	O
than	O
one	O
bus	O
,	O
e.g.	O
,	O
ISA	B-Architecture
,	O
EISA	B-Device
,	O
VESA	O
Local	O
Bus	O
and	O
PCI	B-Protocol
,	O
still	O
sharing	O
the	O
same	O
core	O
logic	O
irrespective	O
of	O
the	O
bus	O
,	O
and	O
such	O
device	B-Application
drivers	I-Application
would	O
also	O
benefit	O
from	O
this	O
same	O
abstraction	O
.	O
</s>
<s>
Thus	O
the	O
rationale	O
of	O
busdma	O
is	O
to	O
facilitate	O
maximum	O
code	O
reuse	O
across	O
a	O
wide	O
range	O
of	O
platforms	B-Device
.	O
</s>
<s>
Circa	O
2006	O
,	O
bus	O
and	O
DMA	O
abstractions	O
made	O
it	O
possible	O
for	O
NetBSD	B-Device
to	O
support	O
50	O
hardware	B-Device
platforms	I-Device
and	O
14	O
CPU	O
architectures	O
out	O
of	O
a	O
single	O
source	O
tree	O
,	O
compared	O
to	O
the	O
forking	O
model	O
used	O
by	O
Linux	B-Application
ports	O
.	O
</s>
<s>
Originally	O
implemented	O
as	O
the	O
"	O
bus_dma	O
"	O
APIs	B-Application
by	O
the	O
developers	O
of	O
the	O
NetBSD	B-Device
operating	B-General_Concept
system	I-General_Concept
,	O
busdma	O
has	O
been	O
adopted	O
by	O
OpenBSD	B-Operating_System
,	O
FreeBSD	B-Operating_System
and	O
their	O
derivatives	O
;	O
with	O
FreeBSD	B-Operating_System
incorporating	O
it	O
under	O
a	O
busdma	O
umbrella	O
(	O
without	O
an	O
underscore	O
)	O
.	O
</s>
<s>
Both	O
NetBSD	B-Device
and	O
OpenBSD	B-Operating_System
have	O
additional	O
"	O
bus_space	O
"	O
APIs	B-Application
that	O
have	O
been	O
amalgamated	O
into	O
the	O
version	O
of	O
busdma	O
incorporated	O
into	O
FreeBSD	B-Operating_System
.	O
</s>
<s>
DragonFly	B-Application
BSD	I-Application
developers	O
are	O
also	O
slowly	O
converting	O
their	O
drivers	O
to	O
use	O
busdma	O
.	O
</s>
