linux-kernel - Re: [PATCH 1/5] iommu: Implement iommu_put_resv_regions

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Message-ID: <20190918153737.dea2z5dddhuus25g@willie-the-truck>
Date:   Wed, 18 Sep 2019 16:37:38 +0100
From:   Will Deacon <will@...nel.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] iommu: Implement iommu_put_resv_regions_simple()

On Thu, Aug 29, 2019 at 01:17:48PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> Implement a generic function for removing reserved regions. This can be
> used by drivers that don't do anything fancy with these regions other
> than allocating memory for them.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/iommu/iommu.c | 19 +++++++++++++++++++
>  include/linux/iommu.h |  2 ++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 0f585b614657..73a2a6b13507 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2170,6 +2170,25 @@ void iommu_put_resv_regions(struct device *dev, struct list_head *list)
>  		ops->put_resv_regions(dev, list);
>  }
>  
> +/**
> + * iommu_put_resv_regions_simple - Reserved region driver helper
> + * @dev: device for which to free reserved regions
> + * @list: reserved region list for device
> + *
> + * IOMMU drivers can use this to implement their .put_resv_regions() callback
> + * for simple reservations. Memory allocated for each reserved region will be
> + * freed. If an IOMMU driver allocates additional resources per region, it is
> + * going to have to implement a custom callback.
> + */
> +void iommu_put_resv_regions_simple(struct device *dev, struct list_head *list)
> +{
> +	struct iommu_resv_region *entry, *next;
> +
> +	list_for_each_entry_safe(entry, next, list, list)
> +		kfree(entry);
> +}
> +EXPORT_SYMBOL(iommu_put_resv_regions_simple);

Can you call this directly from iommu_put_resv_regions() if the function
pointer in ops is NULL? That would save having to plumb the default callback
into a bunch of drivers.

Will