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Date: Tue, 18 Nov 2014 15:32:59 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: "Yun Wu (Abel)" <wuyun.wu@huawei.com>
cc: Jiang Liu <jiang.liu@linux.intel.com>, LKML <linux-kernel@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Grant Likely <grant.likely@linaro.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        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
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On Tue, 18 Nov 2014, Yun Wu (Abel) wrote:

Can you please trim the messages when you're replying?

> The above you described is absolutely right, but not the things I want
> to know. :)
> Take GICv3 ITS for example, it deals with both PCI and non PCI message
> interrupts. IIUC, several irq_chips need to be implemented in the ITS
> driver (i.e. pci_msi_chip, A_msi_chip and B_msi_chip). What should we
> do to the ITS driver if new MSI-capable devices come out?

You seem to miss the stacking here

PCI-MSI	->
A-MSI	->   ITS  -> GIC
B-MSI	->

So each of the device types has its own MSI controller. Each of them
will have their own callbacks and are backed by the underlying ITS/GIC
implementation.

And that's the only sensible solution.

Thanks,

	tglx
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