iommu/core: let drivers know if an iommu fault handler isn't installed

Make report_iommu_fault() return -ENOSYS whenever an iommu fault
handler isn't installed, so IOMMU drivers can then do their own
platform-specific default behavior if they wanted.

Fault handlers can still return -ENOSYS in case they want to elicit the
default behavior of the IOMMU drivers.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3a072596b1b2..bd2d4d2764dd 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -43,6 +43,12 @@ EXPORT_SYMBOL_GPL(iommu_found);
  * iommu_set_fault_handler() - set a fault handler for an iommu domain
  * @domain: iommu domain
  * @handler: fault handler
+ *
+ * This function should be used by IOMMU users which want to be notified
+ * whenever an IOMMU fault happens.
+ *
+ * The fault handler itself should return 0 on success, and an appropriate
+ * error code otherwise.
  */
 void iommu_set_fault_handler(struct iommu_domain *domain,
                                         iommu_fault_handler_t handler)