From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Brezillon Subject: Re: [PATCH v2 2/5] irqchip: Add DT binding doc for dumb demuxer chips Date: Wed, 14 Jan 2015 20:08:09 +0100 Message-ID: <20150114200809.0c16baae@bbrezillon> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20150114185619.GB24989-u4khhh1J0LxI1Ri9qeTfzeTW4wlIGRCZ@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Cooper Cc: Thomas Gleixner , Nicolas Ferre , Jean-Christophe Plagniol-Villard , Alexandre Belloni , "Rafael J. Wysocki" , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org Hi Jason, On Wed, 14 Jan 2015 13:56:19 -0500 Jason Cooper wrote: > Hey Boris, >=20 > 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. > > > >=20 > > > > 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 > > > >=20 > > > > diff --git a/Documentation/devicetree/bindings/interrupt-contro= ller/dumb-demux.txt b/Documentation/devicetree/bindings/interrupt-contr= oller/dumb-demux.txt > > > > new file mode 100644 > > > > index 0000000..1c777ef > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/interrupt-controller/du= mb-demux.txt > > > > @@ -0,0 +1,34 @@ > > > > +* Generic Dumb Interrupt Demultiplexer > > > > + > > > > +This Dumb demultiplixer simply forward all incoming interrupts= to its > > > > +enabled/unmasked children. > > >=20 > > > Please forgive the potentially na=C3=AFve question, but what hard= ware is this > > > describing? > >=20 > > 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). > >=20 > > You can see it as a virtual irqchip provided to address broken hard= ware > > designs. >=20 > Hmm. Well, given tglx's recent reply, I suppose I'll *not* go down t= he > 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... >=20 > However, it would probably be a lot more palatable to the DT maintain= ers > 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. >=20 > 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 hardwar= e, > and that it may be superseded by a better solution later. Actually I thought about changing it to "virtual,dumb-irq-demux" :-). >=20 > 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 --=20 Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html