>gibbs@freefall.FReebsd.ORG (Justin T. Gibbs) wrote:
>
>>Adaptec is no saint, but their attitude is much the same as with NCR.
>[...]
>>They will give you all the documentation to
>>write your own HIM layer (basically what John Aycock and myself have done
>>for the aic7xxx cards and Stephan Esser has done for the NCR).  Neither
>>driver was reversed engineered, they were just more difficult to write.
>
>>As for Buslogic, their cards (until the Flashpoint) do not use downloaded 
>>firmware so the driver can use a well defined, high level, interface to the 
>>card. This is just the same way the 1542 and 1742 cards were designed, and 
>>since both Buslogic and Adaptec can give free software driver writers the 
>>information to talk to that high-level interface without exposing their 
>>"trade secrets" in the firmware, they do so.
>
>Sorry, I didn't get it. Do the Buslogic cards have some kind of
>OS-independent abstraction layer over the hardware? Or is it just the
>hardware that is so simple that no effort needs to be taken to hide the
>details?

The Buslogic cards almost push everything down to the microcontroller on
the SCSI adapter.  You basically give it a command and it does the rest
(including most exception handling).  In many cases, this approach is
inefficient since some operations and decissions are best made by the
kernel driver (because of more RAM, faster processor, or more knowledge
about what else is going on in the system).  For the aic7xxx cards,
you must download your own firmware, decide your own interface to that
firmware, and handle many exceptional conditions up in the kernel.
Since the firmware doesn't have to handle exceptions, its tight, small
and efficient, but the kernel driver must be much, much smarter.

>Thanks
>	Martin
>-- 
>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>Martin Cracauer <cracauer@wavehh.hanse.de>  -  BSD User Group Hamburg
>BSD, Lisp and other programming info http://www.bik-gmbh.de/~cracauer

--
Justin T. Gibbs
===========================================
  FreeBSD: Turning PCs into workstations
===========================================