linux-kernel - RE: [PATCH 02/10] Driver core: Add iommu_ops to bus

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Date:	Thu, 15 Sep 2011 12:45:35 +0000
From:	Sethi Varun-B16395 <B16395@...escale.com>
To:	"Roedel, Joerg" <Joerg.Roedel@....com>
CC:	Joerg Roedel <joro@...tes.org>, Greg KH <gregkh@...e.de>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	David Woodhouse <dwmw2@...radead.org>,
	David Brown <davidb@...eaurora.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 02/10] Driver core: Add iommu_ops to bus_type



> -----Original Message-----
> From: Roedel, Joerg [mailto:Joerg.Roedel@....com]
> Sent: Monday, September 12, 2011 6:06 PM
> To: Sethi Varun-B16395
> Cc: Joerg Roedel; Greg KH; iommu@...ts.linux-foundation.org; Alex
> Williamson; Ohad Ben-Cohen; David Woodhouse; David Brown;
> kvm@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 02/10] Driver core: Add iommu_ops to bus_type
> 
> On Mon, Sep 12, 2011 at 08:08:41AM -0400, Sethi Varun-B16395 wrote:
> > > The IOMMUs are usually devices on the bus itself, so they are
> > > initialized after the bus is set up and the devices on it are
> > > populated.  So the function can not be called on bus initialization
> > > because the IOMMU is not ready at this point.
> > Well, at what point would the add_device_group (referring to patch set
> posted by Alex) call back be invoked?
> 
> The details are up to Alex Williamson. One option is to register a
> notifier for the bus in the iommu_bus_init() function and react to its
> notifications.
> I think in the end we will have a number of additional call-backs in the
> iommu_ops which are called by the notifier (or from the driver-core
> directly) to handle actions like added or removed devices. All the
> infrastructure for that which is implemented in the iommu-drivers today
> will then be in the iommu-core code.
I am not sure If I understand this, but as per your earlier statement iommu is a device on the bus
and its initialization would happen when bus is set up and devices are populated. So, when would device
notifier call an iommu call back?

-Varun
 

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