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Date: Mon, 6 Jun 2005 18:09:11 -0700
From: Andrew Vasquez <andrew.vasquez@qlogic.com>
To: Greg KH <gregkh@suse.de>
Cc: Jeff Garzik <jgarzik@pobox.com>, "David S. Miller" <davem@davemloft.net>,
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       linux-pci@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org,
       ak@suse.de
Subject: Re: [RFC PATCH] PCI: remove access to pci_[enable|disable]_msi() for drivers
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References: <20050607002045.GA12849@suse.de>
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On Mon, 06 Jun 2005, Greg KH wrote:

> 
> Ok, as it seems there is a bit of confusion, here's real code that
> should help explain what I am proposing.  This works on my desktop, but
> I don't think it supports MSI :)
> 
> I'll go dig out an old 4-way AMD box that has MSI to see if this still
> works properly, but comments are welcome.


Thanks for posting some sample code.  Some comments though:

* What if the driver writer does not want MSI enabled for their
  hardware (even though there is an MSI capabilities entry)?  Reasons
  include: overhead involved in initiating the MSI; no support in some
  versions of firmware (QLogic hardware).

* A device (notably, our 4gb PCIe fibre-channel products) can support
  both MSI and MSI-X.  Since the driver has no way of 'disabling' MSI,
  how would it enable MSI-X?

Thanks,
Andrew