Date: 09 Oct 1999 16:26:30 +0000 From: Randell Jesup <rjesup@wgate.com> To: hackers@freebsd.org Subject: Re: CAM-ification - documentation Message-ID: <ybuzoxs33gp.fsf@jesup.eng.tvol.net.jesup.eng.tvol.net> In-Reply-To: "Kenneth D. Merry"'s message of "Fri, 8 Oct 1999 12:54:54 -0600 (MDT)"
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This discussion should probably move to the freebsd-scsi list...
"Kenneth D. Merry" <ken@kdm.org> writes:
>Nick Hibma wrote...
>> Especially some help on the topic of polling would be appreciated.
>> Otherwise I'll have to resort to figuring out how to do things in
>> interrupt context, and that is going to be dirty.
>If you're talking about polling for transaction completion in a device
>driver, my guess is that you're going to have to do things in an interrupt
>context. (Unless you use a kernel process to do it.)
>
>The thing to remember is that when you get CCBs down in a CAM device
>driver, it may well be in an interrupt context. You have to be able to
>deal with that. My guess is that it might be easiest to just use a timeout
>handler to poll the device for completion every so often. A kernel process
>may also be an option, depending on how nasty the device is.
Ick. Polling == bad. Interrupts == good. This isn't a single-
tasking OS ala Win9x. This goes double for SCSI drivers, which are
inherently async and overlapped.
--
Randell Jesup, Worldgate Communications, ex-Scala, ex-Amiga OS team ('88-94)
rjesup@wgate.com
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