Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi_msg

From: Marc Zyngier <marc.zyngier@arm.com>
To: "Yun Wu \(Abel\)" <wuyun.wu@huawei.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Jiang Liu <jiang.liu@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"grant.likely\@linaro.org" <grant.likely@linaro.org>,
	Yingjoe Chen <yingjoe.chen@mediatek.com>,
	Yijing Wang <wangyijing@huawei.com>
Subject: Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi_msg
Date: Tue, 18 Nov 2014 17:21:46 +0000	[thread overview]
Message-ID: <8761ece85x.fsf@approximate.cambridge.arm.com> (raw)
In-Reply-To: <546B5904.6020200@huawei.com> (Yun Wu's message of "Tue, 18 Nov 2014 14:34:44 +0000")

On Tue, Nov 18 2014 at  2:34:44 pm GMT, "Yun Wu (Abel)" <wuyun.wu@huawei.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.

Thanks,

        M.
-- 
Jazz is not dead. It just smells funny.