linux-kernel - Re: PCIE

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Date:	Sat, 26 May 2007 19:03:12 +0400
From:	Manu Abraham <abraham.manu@...il.com>
To:	Roland Dreier <rdreier@...co.com>
CC:	Greg KH <greg@...ah.com>, linux-pci@...ey.karlin.mff.cuni.cz,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: PCIE

Roland Dreier wrote:
>  > I am now wondering whether the usage of MSI would help in this case and
>  > that i should be using enable_msi before request_irq ?
> 
> MSI interrupts are never shared.  So if pci_enable_msi() succeeds, you
> can be sure that the interrupts you get with that IRQ number are
> coming from your device.
> 

i presume then i shouldn't be using IRQF_SHARED, if using MSI.

Another question would be if the device supports multiple messages, MSIX
should be used ?
In such a context, if i request for say more than the messages that i
need, say i request 16 messages, but use only 1 or 2, that does bear any
consequences ?

> But using MSI does not work on all systems, so your driver needs to
> work with standard (possibly shared) INTx interrupts too.  And you
> should probably provide at least a module flag to disable the use of
> MSI, to avoid problems on buggy systems.

I should probably look for CONFIG_PCI_MSI and check whether the system
supports MSI pci_enable_msi() ?

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