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

Lu Baolu
2022-02-15T01:48:44Z

On 2/14/22 8:49 PM, Joerg Roedel wrote:
> 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.
>

We really don't need to WARN_ON intermediate null pointers. But I would
argue that we could add a WARN() on null dev->iommu->iommu_dev->ops, so
that callers have no need to check the returned ops.

Best regards,
baolu