From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752902AbbANTdz (ORCPT ); Wed, 14 Jan 2015 14:33:55 -0500 Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:13272 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751415AbbANTdx convert rfc822-to-8bit (ORCPT ); Wed, 14 Jan 2015 14:33:53 -0500 X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 96.249.243.124 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX18GmtG3u4/byuFgFa1kvSTWwRw5pp8/R4Y= X-DKIM: OpenDKIM Filter v2.0.1 titan E546E646572 Date: Wed, 14 Jan 2015 14:33:32 -0500 From: Jason Cooper To: Boris Brezillon 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: <20150114193332.GC24989@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> <20150114200809.0c16baae@bbrezillon> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20150114200809.0c16baae@bbrezillon> User-Agent: Mutt/1.5.20 (2009-06-14) Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 14, 2015 at 08:08:09PM +0100, Boris Brezillon wrote: > 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... True, I think the issue is more that the DT node doesn't strictly represent a block of IP. We just need a way to make that clear in the binding doc. > > 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" :-). Works for me. :) thx, Jason.