Subject: Re: upcalls from kernel code to user space daemons
From: Bernd Petrovitsch <bernd@firmix.at>
To: Chris Friesen <cfriesen@nortelnetworks.com>
Cc: Oliver Neukum <oliver@neukum.org>, Steve French <smfltc@us.ibm.com>,
       linux-kernel@vger.kernel.org
In-Reply-To: <40CE1F42.1020407@nortelnetworks.com>
References: <200406142341.13340.oliver@neukum.org>
	 <40CE1F42.1020407@nortelnetworks.com>
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Date: Tue, 15 Jun 2004 00:08:45 +0200
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On Mon, 2004-06-14 at 23:57, Chris Friesen wrote:
> Oliver Neukum wrote:
> 
> >  > userspace daemon loops on ioctl()
> >  > kernel portion of ioctl call goes to sleep until something to do
> >  > when needed, fill in data and return to userspace
> >  > userspace does stuff, then passes data back down via ioctl()
> >  > ioctl() puts userspace back to sleep and continues on with other work
> > 
> > You could just as well implement an ordinary read()
> 
> Not quite.  The userspace is passing data down as well.  I don't know how you'd 
> do that with read().

For this you use write().

	Bernd
-- 
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