linux-kernel - Re: MSI messages

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Message-ID: <49460249.8020801@jp.fujitsu.com>
Date:	Mon, 15 Dec 2008 16:07:53 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Grant Grundler <grundler@...isc-linux.org>
CC:	Manu Abraham <abraham.manu@...il.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: MSI messages

Grant Grundler wrote:
> On Sat, Dec 13, 2008 at 01:38:24PM +0400, Manu Abraham wrote:
>> Hi,
>>
>> I am wondering how to handle this:
>>
>> Does the kernel somehow handle MSI message readback from the PCI config space 
>> for the MSI message as described in 6.8.1 of the PCI Bus specification 2.3 or 
>> does a device specific driver have to read the Message Address and Data ?
>>
>> To put it short: i am wondering how i should read the MSI messages.
> 
> The "message" is actually mapped to an the interrupt vector by the core
> generic interrupt handling code in the kernel.
> 
> A "GSI" (Generic Sys Interrupt?) is associated with each entry in
> the MSI-X table. Driver then calls request_irq() to bind an interrupt
> handler to each GSI. So the driver never directly sees the "message".
> 

I think "GSI (Global System Interrupt)" is for identifying the I/O
APIC pin among multiple I/O APICs. Maybe you wanted to mean the
interrupt number managed by kernel (frequently called "IRQ")?
Or am I misunderstanding something?

Thanks,
Kenji Kaneshige

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