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

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Message-ID: <alpine.DEB.2.11.1411181526220.3909@nanos>
Date:	Tue, 18 Nov 2014 15:32:59 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Yun Wu (Abel)" <wuyun.wu@...wei.com>
cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Grant Likely <grant.likely@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	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 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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