kernel subsystems

Dan Williams dcbw at redhat.com
Wed Jun 3 16:33:39 EDT 2009


On Thu, 2009-06-04 at 00:06 +0530, Paresh Sawant wrote:
> Thanks for the information !
> 
> So the mac80211 subsystems could be utilized as a (driver) API to
> develop a driver for a given chipset?

Yes.

> And what kind of details one would need to develop the driver using
> mac80211?

The documentation or spec for the chipset of course.  Then develop using
the existing drivers.  The 'libertastf' driver is probably a pretty
simple driver to look at for starts.  You'll probably want to jump over
to linux-wireless at vger.kernel.org since that's the list where Linux
wireless development is discussed, and where the mac80211 developers
hang out.

Dan


> - Paresh
> 
> On Wed, Jun 3, 2009 at 6:15 PM, Dan Williams <dcbw at redhat.com> wrote:
>         On Wed, 2009-06-03 at 10:58 +0530, Paresh Sawant wrote:
>         > Hi,
>         >
>         > What is the difference in mac80211 and ieee80211 subsystems?
>         
>         
>         mac80211 is a softmac stack, it performs all 802.11 management
>         and data
>         functions in software.
>         
>         ieee80211 is more of a helper library and doesn't implement
>         much of the
>         management function in software, leaving stuff like
>         auth/assoc,
>         beaconing, etc to the firmware.  As such, it's kind of
>         "halfmac".
>         
>         > In future, nl80211 is going to replace the wext, then what
>         is going to
>         > be the  underneath subsystem?
>         
>         
>         nl80211/cfg80211 will replace wext, yes.  They are independent
>         of the
>         underlying 802.11 stack, but are simply a mechanism to
>         *configure* the
>         parameters of that stack.  As such, nl80211/cfg80211 can be
>         used with
>         any driver.  There are proof-of-concept cfg80211 patches for
>         orinoco
>         cards (really popular old FullMAC cards) already, and it's
>         expected that
>         most of the drivers in the kernel will be ported over to
>         cfg80211
>         eventually.
>         
>         This will provide a consistent configuration interface, which
>         is the
>         huge problem with WEXT.  Every driver implements WEXT a little
>         differently, leading to tons of workarounds in wifi control
>         programs
>         like wpa_supplicant and NetworkManager.  cfg80211 will fix all
>         that by
>         providing a WEXT compatbility layer, so all drivers that use
>         cfg80211
>         will work pretty much the same.
>         
>         Dan
>         
>         
> 
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