linux-kernel - Re: [PATCHv7 05/12] iommu/core: add ops->{bound,unbind}

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Message-ID: <20131230134522.GB2799@8bytes.org>
Date:	Mon, 30 Dec 2013 14:45:23 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Hiroshi Doyu <hdoyu@...dia.com>
Cc:	Stephen Warren <swarren@...dotorg.org>, swarren@...dia.com,
	will.deacon@....com, grant.likely@...aro.org,
	thierry.reding@...il.com, robherring2@...il.com,
	mark.rutland@....com, devicetree@...r.kernel.org,
	lorenzo.pieralisi@....com, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org, galak@...eaurora.org,
	linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv7 05/12] iommu/core: add ops->{bound,unbind}_driver()

On Thu, Dec 12, 2013 at 09:57:06AM +0200, Hiroshi Doyu wrote:
> ops->{bound,unbind}_driver() functions are called at
> BUS_NOTIFY_{BOUND,UNBIND}_DRIVER respectively.
> 
> This is necessary to control the device population order. IOMMU master
> devices depend on an IOMMU device instanciation. IOMMU master devices
> can be registered to an IOMMU only after it's successfully
> populated. This IOMMU registration is done via
> ops->bound_driver(). Currently this population can be deferred if
> depending IOMMU device hasn't yet been populated in driver core. This
> cannot be done via ops->add_device() since after add_device() device's
> population/instanciation can be still deferred via probe().

How about doing dependency checking in the add/remove_device callbacks
instead? When a device is about to be initialized where the IOMMU is not
set up yet, just setup the IOMMU first before initializing the device?


	Joerg


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