linux-kernel - Re: [PATCH 2/2 v5] irqchip/Layerscape: Add SCFG MSI controller support

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Date:	Wed, 23 Mar 2016 11:36:23 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Alexander Stein <alexander.stein@...tec-electronic.com>
Cc:	linux-kernel@...r.kernel.org,
	Minghuan Lian <Minghuan.Lian@....com>,
	linux-arm-kernel@...ts.infradead.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Roy Zang <roy.zang@....com>, Mingkai Hu <mingkai.hu@....com>,
	Stuart Yoder <stuart.yoder@....com>,
	Yang-Leo Li <leoyang.li@....com>
Subject: Re: [PATCH 2/2 v5] irqchip/Layerscape: Add SCFG MSI controller
 support

On 23/03/16 11:19, Alexander Stein wrote:
> On Wednesday 23 March 2016 11:08:04, Marc Zyngier wrote:
>>> Using an intel e1000e card which uses 3 MSIs. But the IRQ numbers are a bit strange though:
>>>> grep eth3 /proc/interrupts
>>>>
>>>>  63:         49          0       MSI 134742016 Edge      eth3-rx-0
>>>>  64:          3          0       MSI 134742017 Edge      eth3-tx-0
>>>>  65:          4          0       MSI 134742018 Edge      eth3
>>
>> This is a virtual interrupt number (despite being displayed as a hwirq),
>> computed from the PCI requester ID and the MSI index. You shouldn't
>> infer anything from it.
> 
> Why show it anyway then if you can't infer anything?

Because this field conveys meaningful information for almost every other
interrupt in the system. I'm not going to special case the MSI layer
just on the ground that it may not be always useful (and in fact it *is*
useful if you know what the generating function is).

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