Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc_user op

On 2023/9/21 15:51, Yi Liu wrote:

+/**

• • iommu_copy_user_data - Copy iommu driver specific user space data
• • @dst_data: Pointer to an iommu driver specific user data that is defined in

• •        include/uapi/linux/iommufd.h
    

• • @src_data: Pointer to a struct iommu_user_data for user space data info
• • @data_len: Length of current user data structure, i.e. sizeof(struct _dst)
• • @min_len: Initial length of user data structure for backward compatibility.

• •       This should be offsetofend using the last member in the user data
    

• •       struct that was initially added to include/uapi/linux/iommufd.h
    

• */

+static inline int iommu_copy_user_data(void *dst_data,

• 		       const struct iommu_user_data *src_data,
  

• 		       size_t data_len, size_t min_len)
  

+{

• if (WARN_ON(!dst_data || !src_data))

• return -EINVAL;
  

• if (src_data->len < min_len || data_len < src_data->len)

• return -EINVAL;
  

• return copy_struct_from_user(dst_data, data_len,

• 		     src_data->uptr, src_data->len);
  

+}

I am not sure that I understand the purpose of "min_len" correctly. It seems like it would always be equal to data_len?

Or, it means the minimal data length that the iommu driver requires?

Best regards, baolu