Re: [PATCH net-next 1/2] net: renesas: rswitch: use per-port irq handlers

[Nikita Yushchenko <nikita.yoush@cogentembedded.com>]

>>> Sorry, but I can't find where this property is documented?
>>
>> I will add this.
> 
> Device tree properties should be a hardware description. However,
> about the "irq-index", it seems a software configuration. So, even if we would
> like to submit such a patch to add the property, it will be rejected.

Hmm...

Indeed it is a software configuration.

I was not aware of such a rule.

I believe there shall be plenty of situations when a per-hardware-node software configuration is 
desired. What method do other use, if not device tree?

> Also, even if we can add a new device tree property, we should keep backward compatible.
> However, this patch seems to break a backward compatibility.

It does not.
If this new property is not defined, then it will default to 0, which will result exactly into previous 
behavior.

> Unfortunately, I don't have alternative solutions how to configurate per-port irq though...
> # Maybe configfs??

Looks like overengineering...

Perhaps can just hardcode irq-index N for port N for now. But then, flexibility will be lost.

In more complex situations that I target in future, some of 8 GWCA interrupts will be given to virtual 
machines (and/or Xen domains) to serve virtual port frontends, and some will be needed for virtual port 
backends.  So 8 will be not enough to have a per-consumer interrupt, and some configuration method is 
needed.

Nikita