Subject: [PATCH v3 1/3] IRQ/Gic-V3: Add mbigen driver to support mbigen interrupt controller

From: [email-masked] (majun (F))
Date: Thu, 16 Jul 2015 17:22:05 +0800

? 2015/7/16 16:52, Marc Zyngier ??:
> On 16/07/15 09:35, majun (F) wrote:

>>> I'm a bit puzzled.
>>
>> For interrupts connect to mbigen , the interrupt trigger type, device id and
>> event id value are encoded in mbigen chip already.
>>
>> There are two types of mbigen node within a mbigen chip.
>> Type1: event id valud can't be programmed.
>> Type2: event id value can be programmed.
>>
>> For example: An device with 5 interrupts connected to Mbigen node
>> type 1.The default event id vlaue encoded in mbigen chip for these 5 interrupt
>> is from 0 to 4.
>>
>> Because the event id value can't be programmed, we need to define all of
>> 5 interrupts in dts file so that these 5 interrupt has
> 
> You can define what you want in the device tree, the ITS doesn't care!
> Nothing in the ITS code parses this property, and there is absolutely
> zero chance that the even the ITS has allocated will actually match what
> you expect.
> 
> The ITS *relies* on the principle that the evenID can be programmed,
> just like any MSI controller relies on the device to be programmed with
> whatever payload has been provided. If all of a sudden we have to
> support HW that has its own view of the payload, what you have here will
> simply not work.
> 
"If all of a sudden we have to
 support HW that has its own view of the payload, what you have here will
 simply not work."

I am not very unstand this case, would you please explain this more detail?
Thanks!