From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Schwebel Subject: Re: Triggering UserCode from KernelModule (IRQ) Date: Wed, 22 Apr 2009 21:59:56 +0200 Message-ID: <20090422195956.GM5367@pengutronix.de> References: <6669682.1240409688443.JavaMail.ngmail@webmail19.ha2.local> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Cc: linux-rt-users@vger.kernel.org To: "M. Koehrer" Return-path: Received: from metis.ext.pengutronix.de ([92.198.50.35]:50382 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756608AbZDVT75 (ORCPT ); Wed, 22 Apr 2009 15:59:57 -0400 Content-Disposition: inline In-Reply-To: <6669682.1240409688443.JavaMail.ngmail@webmail19.ha2.local> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Wed, Apr 22, 2009 at 04:14:48PM +0200, M. Koehrer wrote: > However, there is one operation mode that uses interrupts to signal > incoming data. The interrupt handler is realized as a tiny kernel > module (that one that provides also the mmap for the user mode > application). Now I am not sure how the signalling of the IRQ from > kernel to user mode could be realized best (in terms of low latency). > > The "classical" approach for this task is to provide a character > driver with a .poll file operation. In Xenomai I could use a semaphore > that was accessible from kernel and user space for this. What is the > best way in the RT_PREEMPT "world"? UIO might be a good choice here, the rest is giving the interrupt handler and the processes the right priorities. rsc -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |