From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752919AbbANTIR (ORCPT ); Wed, 14 Jan 2015 14:08:17 -0500 Received: from down.free-electrons.com ([37.187.137.238]:46975 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751241AbbANTIP convert rfc822-to-8bit (ORCPT ); Wed, 14 Jan 2015 14:08:15 -0500 Date: Wed, 14 Jan 2015 20:08:09 +0100 From: Boris Brezillon To: Jason Cooper Cc: Thomas Gleixner , Nicolas Ferre , Jean-Christophe Plagniol-Villard , Alexandre Belloni , "Rafael J. Wysocki" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree@vger.kernel.org Subject: Re: [PATCH v2 2/5] irqchip: Add DT binding doc for dumb demuxer chips Message-ID: <20150114200809.0c16baae@bbrezillon> In-Reply-To: <20150114185619.GB24989@titan.lakedaemon.net> References: <1421174781-4340-1-git-send-email-boris.brezillon@free-electrons.com> <1421174781-4340-3-git-send-email-boris.brezillon@free-electrons.com> <20150113190050.GZ24989@titan.lakedaemon.net> <20150113215207.185d92b4@bbrezillon> <20150114185619.GB24989@titan.lakedaemon.net> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jason, On Wed, 14 Jan 2015 13:56:19 -0500 Jason Cooper wrote: > Hey Boris, > > On Tue, Jan 13, 2015 at 09:52:07PM +0100, Boris Brezillon wrote: > > On Tue, 13 Jan 2015 14:00:50 -0500 Jason Cooper wrote: > > > On Tue, Jan 13, 2015 at 07:46:18PM +0100, Boris Brezillon wrote: > > > > Add documentation for the dumb demuxer. > > > > > > > > Signed-off-by: Boris Brezillon > > > > --- > > > > .../bindings/interrupt-controller/dumb-demux.txt | 34 ++++++++++++++++++++++ > > > > 1 file changed, 34 insertions(+) > > > > create mode 100644 Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt > > > > > > > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt b/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt > > > > new file mode 100644 > > > > index 0000000..1c777ef > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt > > > > @@ -0,0 +1,34 @@ > > > > +* Generic Dumb Interrupt Demultiplexer > > > > + > > > > +This Dumb demultiplixer simply forward all incoming interrupts to its > > > > +enabled/unmasked children. > > > > > > Please forgive the potentially naïve question, but what hardware is this > > > describing? > > > > That's not a real hardware per se, but on some hardware (like at91 SoCs) > > some IRQ line are shared by several peripherals, and this dumb > > demultiplex is here to represent such shared irq lines which cannot be > > easily demultiplexed (because they do not provide a 'cause' > > register). > > > > You can see it as a virtual irqchip provided to address broken hardware > > designs. > > Hmm. Well, given tglx's recent reply, I suppose I'll *not* go down the > rabbit hole of "the DT is for describing hardware." :-P Actually I'm a bit surprised no one else already mentioned that :-) (I thought this would be the first complain regarding this dumb irq demux chip). Anyway, IMHO, this can be considered as hardware description since these irq-lines are really multiplexed into a single one... > > However, it would probably be a lot more palatable to the DT maintainers > if we at least change the compatible to prepend "linux,". This way, if > someone does come up with a better solution down the road, it will be > much easier to deprecate the binding. > > I would also be amenable to "virt,", or "hack,", or even > "work-around-piss-poor-hw,". Basically, anything that would indicate to > consumers of the DT that this is not a true reflection of the hardware, > and that it may be superseded by a better solution later. Actually I thought about changing it to "virtual,dumb-irq-demux" :-). > > It would also be helpful to explain the situation more fully in the > binding document. Sure, I'll add a few lines to describe what this irqchip really is. Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com