From owner-freebsd-current  Wed Jun 10 23:44:34 1998
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Received: (from majordom@localhost)
          by hub.freebsd.org (8.8.8/8.8.8) id XAA05183
          for freebsd-current-outgoing; Wed, 10 Jun 1998 23:44:34 -0700 (PDT)
          (envelope-from owner-freebsd-current@FreeBSD.ORG)
Received: from labinfo.iet.unipi.it (labinfo.iet.unipi.it [131.114.9.5])
          by hub.freebsd.org (8.8.8/8.8.8) with SMTP id XAA05159
          for <current@FreeBSD.org>; Wed, 10 Jun 1998 23:44:31 -0700 (PDT)
          (envelope-from luigi@labinfo.iet.unipi.it)
Received: from localhost (luigi@localhost) by labinfo.iet.unipi.it (8.6.5/8.6.5) id HAA21914; Thu, 11 Jun 1998 07:07:52 +0200
From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Message-Id: <199806110507.HAA21914@labinfo.iet.unipi.it>
Subject: Re: floating point usage within the kernel - howto ?
To: mike@smith.net.au (Mike Smith)
Date: Thu, 11 Jun 1998 07:07:51 +0200 (MET DST)
Cc: mike@smith.net.au, current@FreeBSD.ORG
In-Reply-To: <199806110524.WAA01035@antipodes.cdrom.com> from "Mike Smith" at Jun 10, 98 10:24:27 pm
X-Mailer: ELM [version 2.4 PL23]
Content-Type: text
Sender: owner-freebsd-current@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

> > task to the timer interrupt. I am trying to push them to use FreeBSD
> > (and an LKM for this module) so that they can easily access the
> > controller across the network or via the web, use high level stuff
> > for visualization, etc.
> 
> A worthy goal.  They're not interested in using a "real" motor 
> controller card?  

they do it for real stuff of course but this opens other problems like
the sw. development which usually runs under dos/windows (what else!),
communicating withthe controller across a serial line, etc.

> > For sure they can do fixed point, but if i can find a solution for
> > 'save_fp_regs()/restore_fp_regs()' this might have other uses as well.
> 
> The problem is mostly just one of dealing with the FP context switch; 

ok, i will browse through the sources. i have seen a reference to
npxsave which could help.

> IMHO, you'd be better of with them using rtprio() and running the 
> control applicaton in user-space, especially if they were previously 
> using the 18Hz timer resolution.  It doesn't sound like anything other 
> than the hardware access needs to be in the kernel at all.

that's an alternative but i am just not sure how much overhead there
would be (we plan to use up to HZ=1000 and run at every tick; the original
application used to run at 100-200 hz they are telling me, using a
timer on the AD/DA card.)

	thanks
	luigi

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message