Re: [PATCH v6 3/4] iommufd: Add IOMMU_GET_HW_INFO

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Aug 09, 2023 at 06:16:19PM +0800, Baolu Lu wrote:
> On 2023/8/8 23:35, Yi Liu wrote:
> > +static int iommufd_fill_hw_info(struct device *dev, void __user *user_ptr,
> > +				unsigned int *length, u32 *type)
> > +{
> > +	const struct iommu_ops *ops;
> > +	unsigned int data_len;
> > +	void *data;
> > +	int rc = 0;
> > +
> > +	ops = dev_iommu_ops(dev);
> > +	if (!ops->hw_info) {
> > +		*length = 0;
> > +		*type = IOMMU_HW_INFO_TYPE_NONE;
> > +		return 0;
> > +	}
> > +
> > +	data = ops->hw_info(dev, &data_len, type);
> > +	if (IS_ERR(data))
> > +		return PTR_ERR(data);
> > +
> > +	/*
> > +	 * drivers that have hw_info callback should have a unique
> > +	 * iommu_hw_info_type.
> > +	 */
> > +	if (WARN_ON_ONCE(*type == IOMMU_HW_INFO_TYPE_NONE)) {
> > +		rc = -ENODEV;
> > +		goto err_free;
> > +	}
> > +
> > +	*length = min(*length, data_len);
> > +	if (copy_to_user(user_ptr, data, *length)) {
> 
> copy_to_user() returns the number of bytes that were successfully
> copied, right?

It returns length on failure and 0 on success

Jason