linux-kernel - Re: [PATCHv4] uio: add generic driver for PCI 2.3 devices

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Date:	Mon, 20 Jul 2009 10:17:02 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>, anthony@...emonkey.ws,
	avi@...hat.com, kvm@...r.kernel.org, chrisw@...hat.com,
	hjk@...utronix.de, gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4] uio: add generic driver for PCI 2.3 devices

On Wed, 15 Jul 2009 23:39:11 +0200
"Hans J. Koch" <hjk@...utronix.de> wrote:

> On Wed, Jul 15, 2009 at 11:13:40PM +0300, Michael S. Tsirkin wrote:
> > This adds a generic uio driver that can bind to any PCI device.
> > First user will be virtualization where a qemu userspace process
> > needs to give guest OS access to the device.
> > 
> > Interrupts are handled using the Interrupt Disable bit in the PCI
> > command register and Interrupt Status bit in the PCI status
> > register.  All devices compliant to PCI 2.3 (circa 2002) and all
> > compliant PCI Express devices should support these bits.  Driver
> > detects this support, and won't bind to devices which do not
> > support the Interrupt Disable Bit in the command register.
> > 
> > It's expected that more features of interest to virtualization will
> > be added to this driver in the future. Possibilities are: mmap for
> > device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.
> 
> Well, I'm not enough of a PCI expert to tell whether your 2.3-test
> works or not (can it have side effects, e.g. trigger an interrupt
> when you toggle that bit?). I've added Jesse Barnes to Cc: since you
> modify a PCI core header file. If there are no objections from the
> PCI people, I guess we can take this.

pci_reg.h portion looks fine to me, and only supporting devices with
the interrupt disable bit certainly simplifies things.  There were some
other questions on the thread though (like Greg's similar driver); not
sure if you've answered those yet.

-- 
Jesse Barnes, Intel Open Source Technology Center
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