View source for Busdma

{{Short description|Application programming interfaces for BSD operating systems}}
{{lowercase title}}
In [[computing]], '''busdma''', '''bus_dma''' and '''bus_space''' is a set of [[application programming interface]]s designed to help make [[device driver]]s less dependent on platform-specific code, thereby allowing the host [[operating system]] to be more easily [[portability (software)|ported]] to new computer hardware.{{r|usenix98|informit-2006}}  This is accomplished by having abstractions for [[direct memory access]] (DMA) mapping across popular machine-independent [[computer bus]]es like [[Peripheral Component Interconnect|PCI]], which are used on distinct architectures from [[IA-32]] (NetBSD/i386) to [[DEC Alpha]] (NetBSD/alpha).{{r|usenix98}}  Additionally, some devices may come in multiple flavours supporting more than one bus, e.g., [[Industry Standard Architecture|ISA]], [[Extended Industry Standard Architecture|EISA]], [[VESA Local Bus]] and [[Peripheral Component Interconnect|PCI]], still sharing the same core logic irrespective of the bus, and such device drivers would also benefit from this same abstraction.{{r|usenix98|p=§1.2|q=1.2.  Bus details}}  Thus the rationale of busdma is to facilitate maximum [[code reuse]] across a wide range of [[platform (computing)|platforms]].{{r|usenix98|p=§5|q=5.  Conclusions}}

Circa 2006, bus and DMA abstractions made it possible for NetBSD to support 50 hardware platforms and 14 CPU architectures out of a single source tree, compared to the [[Fork (software development)|fork]]ing model used by [[Linux]] ports.{{r|informit-2006}}

Originally implemented as the "bus_dma" APIs by the developers of the [[NetBSD]] operating system,{{r|usenix98|bus_dma}} busdma has been adopted by [[OpenBSD]], [[FreeBSD]] and their derivatives; with FreeBSD incorporating it under a '''busdma''' umbrella (without an underscore). Both NetBSD and OpenBSD have additional "bus_space" APIs{{r|bus_space}} that have been amalgamated into the version of busdma incorporated into FreeBSD. [[DragonFly BSD]] developers are also slowly converting their drivers to use busdma.

==References==
{{Reflist |refs=

<ref name=usenix98>{{cite conference
|author= Jason R Thorpe |author2= NASA Ames Research Center |author2-link= NASA Ames Research Center |date= 1998
|url= https://www.usenix.org/legacy/publications/library/proceedings/usenix98/freenix/thorpe_dma.pdf
|title= A Machine-Independent DMA Framework for NetBSD
|conference= Proceedings of the FREENIX Track: 1998 USENIX Annual Technical Conference
|conference-url= https://www.usenix.org/legacy/publications/library/proceedings/usenix98/
|publisher= [[USENIX Annual Technical Conference|USENIX]]
}}
*{{cite journal |title=A Machine-Independent DMA Framework for Net BSD |url=https://www.usenix.org/conference/1998-usenix-annual-technical-conference/machine-independent-dma-framework-net-bsd |website=Usenix|year=1998 }}</ref>

<ref name=bus_dma>{{cite web
|author1= Jason R Thorpe |author2= NASA Ames Research Center |author2-link= NASA Ames Research Center |date= 1997
|url= http://bxr.su/n/share/man/man9/bus_dma.9
|title= bus_dma, … — Bus and Machine Independent DMA Mapping Interface
|website= BSD Cross Reference
|publisher= [[NetBSD]], [[FreeBSD]], [[OpenBSD]], [[DragonFly BSD]]
}}
*{{cite book |section=BUS_DMA(9) |title=FreeBSD Manual Pages |url=http://mdoc.su/FreeBSD/bus_dma.9}}
*{{cite book |section=BUS_DMAMAP_CREATE(9) |title=OpenBSD manual page server |url=http://mdoc.su/OpenBSD/bus_dma.9}}
*{{cite book |section=BUS_DMA(9) |title=DragonFly On-Line Manual Pages |url=http://mdoc.su/DragonFly/bus_dma.9}}</ref>

<ref name=bus_space>{{cite web
|author= Christopher G. Demetriou |date= 1997
|url= http://bxr.su/n/share/man/man9/bus_space.9
|title= bus_space, … — bus space manipulation functions
|website= BSD Cross Reference
|publisher= [[NetBSD]], [[FreeBSD]], [[OpenBSD]], [[DragonFly BSD]]
}}
*{{cite book |section=BUS_SPACE(9) |title=FreeBSD Manual Pages |url=https://www.freebsd.org/cgi/man.cgi?query=bus_space&sektion=9}}
*{{cite book |section=BUS_SPACE(9) |title=OpenBSD manual page server |url=http://man.openbsd.org/bus_space.9}}
*{{cite book |section=BUS_SPACE(9) |title=DragonFly On-Line Manual Pages |url=https://www.dragonflybsd.org/cgi/web-man?command=bus_space&section=9}}</ref>

<ref name= informit-2006 >{{cite web
|author= David Chisnall |date= 2006-10-06
|url= http://www.informit.com/articles/printerfriendly/655422
|title= NetBSD: Not Just for Toasters 
|publisher= [[Prentice Hall Professional]]
|website= [[InformIT (publisher)|InformIT]]
|access-date= 2019-07-25
}}</ref>

}}

==External links==
*<code>{{URL|http://mdoc.su/-/bus_dma.9|bus_dma(9)}}</code> — NetBSD, FreeBSD, OpenBSD and DragonFly BSD Kernel Developer's [[man page|Manual]]s
*<code>{{URL|http://mdoc.su/-/bus_space.9|bus_space(9)}}</code> — NetBSD, FreeBSD, OpenBSD and DragonFly BSD Kernel Developer's [[man page|Manual]]s
*[http://www.freebsd.org/projects/busdma/ FreeBSD busdma and SMPng driver conversion project page] {{Webarchive|url=https://web.archive.org/web/20100729125804/http://www.freebsd.org/projects/busdma/ |date=2010-07-29 }}
*{{URL|https://wiki.freebsd.org/UnifiedBusDma}}

{{NetBSD}}
{{FreeBSD}}
{{OpenBSD}}
{{DragonFly}}

[[Category:Application programming interfaces]]
[[Category:BSD software]]
[[Category:NetBSD]]
[[Category:FreeBSD]]
[[Category:OpenBSD]]
[[Category:DragonFly BSD]]
[[Category:Operating system APIs]]
[[Category:Operating system technology]]


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