From: Jason Gunthorpe jgg@nvidia.com Sent: Thursday, July 27, 2023 10:43 PM
On Thu, Jul 27, 2023 at 07:57:57AM +0000, Tian, Kevin wrote:
From: Liu, Yi L yi.l.liu@intel.com Sent: Monday, July 24, 2023 7:00 PM
@@ -252,11 +258,20 @@ struct iommu_iotlb_gather {
- @remove_dev_pasid: Remove any translation configurations of a specific
pasid, so that any DMA transactions with this pasidwill be blocked by the hardware.
- @hw_info_type: One of enum iommu_hw_info_type defined in
include/uapi/linux/iommufd.h. It is used to tag the type
of data returned by .hw_info callback. The drivers that
support .hw_info callback should define a unique type
in include/uapi/linux/iommufd.h. For the drivers that do
not implement .hw_info callback, this field is
IOMMU_HW_INFO_TYPE_NONE which is 0. Hence, such drivers
do not need to care this field.every time looking at this field the same question came out why it is required (and looks I forgot your previous response).
The major reason is that not every driver implements the hw_info callback.
e.g. why cannot the type be returned in @hw_info():
void *(*hw_info)(struct device *dev, u32 *length, int *type);
u32 *type
NULL callback implies IOMMU_HW_INFO_TYPE_NONE.
If every one of these queries has its own type it makes sense
Though, is it not possible that we can have a type for the entire driver?
Not quite sure if I got your point. Is it acceptable to define the callabck in the current version? or Kevin's suggestion makes more sense?
Regards, Yi Liu