Re: [PATCH v3 07/10] iommu: Use right way to retrieve iommu_ops

[Joerg Roedel]

On Mon, Feb 14, 2022 at 09:55:35AM +0800, Lu Baolu wrote:
> +static inline const struct iommu_ops *dev_iommu_ops(struct device *dev)
> +{
> +	/*
> +	 * Assume that valid ops must be installed if iommu_probe_device()
> +	 * has succeeded. The device ops are essentially for internal use
> +	 * within the IOMMU subsystem itself, so we should be able to trust
> +	 * ourselves not to misuse the helper.
> +	 */
> +	WARN_ON(!dev || !dev->iommu || !dev->iommu->iommu_dev ||
> +		!dev->iommu->iommu_dev->ops);

There is no need for this WARN_ON, the code will oops anyway when one of
the pointers checked here is NULL.