linux-kernel - Re: [PATCHv7 02/12] iommu/of: introduce a global iommu device list

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Message-ID: <52AF474F.7080701@wwwdotorg.org>
Date:	Mon, 16 Dec 2013 11:32:47 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Hiroshi Doyu <hdoyu@...dia.com>, swarren@...dia.com,
	will.deacon@....com, grant.likely@...aro.org,
	thierry.reding@...il.com, robherring2@...il.com, joro@...tes.org
CC:	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 02/12] iommu/of: introduce a global iommu device list

On 12/12/2013 12:57 AM, Hiroshi Doyu wrote:
> This enables to find an populated IOMMU device via a device node. This
> can be used to see if an dependee IOMMU is populated or not to keep
> correct device population order. Client devices need to wait an IOMMU
> to be populated.
> 
> Suggested by Thierry Reding and copied his example code.

> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c

> +static struct iommu *of_find_iommu_by_node(struct device_node *np)
> +{
> +	struct iommu *iommu;
> +
> +	mutex_lock(&iommus_lock);
> +	list_for_each_entry(iommu, &iommus_list, list) {
> +		if (iommu->dev->of_node == np) {
> +			mutex_unlock(&iommus_lock);

Now that the list is unlocked, the IOMMU could be removed from the list,
and the driver unregistered. Should you do something like
iommu_get(iommu); before the mutex_unlock() call, and call iommu_put()
somewhere (i.e. in the next patch ...)?
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