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 [off-list ref] wrote:

quoted

On Tue, Jan 13, 2015 at 07:46:18PM +0100, Boris Brezillon wrote:

quoted

Add documentation for the dumb demuxer.

Signed-off-by: Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTGGXanvQGlWp@public.gmane.orgm>
---
 .../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

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and that it may be superseded by a better solution later.

It would also be helpful to explain the situation more fully in the
binding document.

thx,

Jason.
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