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Date:   Tue, 11 Jul 2023 14:05:03 -0700
From:   Jacob Pan <jacob.jun.pan@linux.intel.com>
To:     Lu Baolu <baolu.lu@linux.intel.com>
Cc:     Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Kevin Tian <kevin.tian@intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Nicolin Chen <nicolinc@nvidia.com>,
        Yi Liu <yi.l.liu@intel.com>, iommu@lists.linux.dev,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH 4/9] iommu: Change the return value of dev_iommu_get()
Message-ID: <20230711140503.65e70501@jacob-builder>
In-Reply-To: <20230711010642.19707-5-baolu.lu@linux.intel.com>
References: <20230711010642.19707-1-baolu.lu@linux.intel.com>
        <20230711010642.19707-5-baolu.lu@linux.intel.com>
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Hi BaoLu,

On Tue, 11 Jul 2023 09:06:37 +0800, Lu Baolu <baolu.lu@linux.intel.com>
wrote:

> Make dev_iommu_get() return 0 for success and error numbers for failure.
> This will make the code neat and readable. No functionality changes.
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/iommu/iommu.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 41328f03e8b4..65895b987e22 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -287,20 +287,20 @@ void iommu_device_unregister(struct iommu_device
> *iommu) }
>  EXPORT_SYMBOL_GPL(iommu_device_unregister);
>  
> -static struct dev_iommu *dev_iommu_get(struct device *dev)
> +static int dev_iommu_get(struct device *dev)
>  {
>  	struct dev_iommu *param = dev->iommu;
>  
>  	if (param)
> -		return param;
> +		return 0;
>  
>  	param = kzalloc(sizeof(*param), GFP_KERNEL);
>  	if (!param)
> -		return NULL;
> +		return -ENOMEM;
>  
>  	mutex_init(&param->lock);
>  	dev->iommu = param;
> -	return param;
> +	return 0;
>  }
>  
>  static void dev_iommu_free(struct device *dev)
> @@ -351,10 +351,9 @@ static int __iommu_probe_device(struct device *dev,
> struct list_head *group_list
>  	 * but for now enforcing a simple global ordering is fine.
>  	 */
>  	mutex_lock(&iommu_probe_device_lock);
> -	if (!dev_iommu_get(dev)) {
> -		ret = -ENOMEM;
> +	ret = dev_iommu_get(dev);
> +	if (ret)
>  		goto err_unlock;
> -	}
>  
>  	if (!try_module_get(ops->owner)) {
>  		ret = -EINVAL;
> @@ -2751,12 +2750,14 @@ int iommu_fwspec_init(struct device *dev, struct
> fwnode_handle *iommu_fwnode, const struct iommu_ops *ops)
>  {
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> +	int ret;
>  
>  	if (fwspec)
>  		return ops == fwspec->ops ? 0 : -EINVAL;
>  
> -	if (!dev_iommu_get(dev))
> -		return -ENOMEM;
> +	ret = dev_iommu_get(dev);
> +	if (ret)
> +		return ret;
>  
>  	/* Preallocate for the overwhelmingly common case of 1 ID */
>  	fwspec = kzalloc(struct_size(fwspec, ids, 1), GFP_KERNEL);

Reviewed-by: Jacob Pan <jacob.jun.pan@linux.intel.com>

Thanks,

Jacob