linux-kernel - Re: [PATCH] ALSA: hda-intel - Disable MSI support by default

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Message-ID: <455A9664.50404@garzik.org>
Date:	Tue, 14 Nov 2006 23:24:04 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	David Miller <davem@...emloft.net>
CC:	torvalds@...l.org, linux-kernel@...r.kernel.org, tiwai@...e.de
Subject: Re: [PATCH] ALSA: hda-intel - Disable MSI support by default

David Miller wrote:
> Is this absolutely true?  I've never been sure about this point, and I
> was rather convinced after reading various documents that once you
> program up the MSI registers to start generating MSI this implicitly
> disabled INTX and this was even in the PCI specification.
> 
> It would be great to get a definitive answer on this.
> 
> If it is mandatory, perhaps the driver shouldn't be doing it and
> rather the PCI layer MSI enabling should.


I can't answer for the spec, but at least two independent device vendors 
recommended to write an MSI driver that way (disable intx, enable msi).

Completely independent of MSI though, a PCI 2.2 compliant driver should 
be nice and disable intx on exit, just to avoid any potential interrupt 
hassles after driver unload.  And of course be aware that it might need 
to enable intx upon entry.

	Jeff


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