linux-kernel - Re: [PATCH v2 2/5] irqchip: Add DT binding doc for dumb demuxer chips

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150114200809.0c16baae@bbrezillon>
Date:	Wed, 14 Jan 2015 20:08:09 +0100
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Jason Cooper <jason@...edaemon.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/5] irqchip: Add DT binding doc for dumb demuxer
 chips

Hi Jason,

On Wed, 14 Jan 2015 13:56:19 -0500
Jason Cooper <jason@...edaemon.net> 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 <jason@...edaemon.net> 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 <boris.brezillon@...e-electrons.com>
> > > > ---
> > > >  .../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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/