linux-kernel - Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi

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Message-ID: <546C1148.4080102@huawei.com>
Date:	Wed, 19 Nov 2014 11:40:56 +0800
From:	"Yun Wu (Abel)" <wuyun.wu@...wei.com>
To:	Marc Zyngier <marc.zyngier@....com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Bjorn Helgaas" <bhelgaas@...gle.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	"Yijing Wang" <wangyijing@...wei.com>
Subject: Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi_msg

On 2014/11/19 1:21, Marc Zyngier wrote:

> On Tue, Nov 18 2014 at  2:34:44 pm GMT, "Yun Wu (Abel)" <wuyun.wu@...wei.com> wrote:
>> On 2014/11/18 22:19, Thomas Gleixner wrote:
>>
>>> On Tue, 18 Nov 2014, Yun Wu (Abel) wrote:
>>>> On 2014/11/18 21:43, Jiang Liu wrote:
>>>>> 	We provide an irq_chip for each type of interrupt controller
>>>>> instead of devices. For the example mentioned above, if device A
>>>>> and Group B has different interrupt controllers, we just need to
>>>>> implement irq_chip_A and irq_chip_B and set irq_chip.irq_write_msi_msg()
>>>>> to suitable callbacks.
>>>>> 	The framework already achieves what you you want:)
>>>>
>>>> What if device A and group B have the same interrupt controller?
>>>
>>> Well, if write_msg() is different they are hardly the same.
>>>
>>
>> The GICv3 ITS now deals with both PCI and non PCI message interrupts.
>> We can't require the new devices behave writing message in a same way.
>> What we can do is to abstract all the endpoints' behavior, and I
>> provided one abstraction in an earlier reply.
> 
> This is why the framework gives you the opportunity to provide methods
> that:
> - compose the message
> - program the message into the device
> 
> None of that has to be PCI specific, and gives you a clean
> abstraction. The framework only gives you a number of shortcuts for PCI
> MSI, because that's what most people care about.
> 

Indeed, and I never said Jiang's patches don't work, I was just thinking
that they were not that perfect.

Thanks,
	Abel

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