[PATCH v1 05/10] iommufd/viommu: Add iommufd_vdev_id_to_dev helper

[Nicolin Chen <nicolinc@xxxxxxxxxx>]

This helps drivers to get the dev pointer held by the vdev_id structure.

Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 drivers/iommu/iommufd/viommu_api.c | 14 ++++++++++++++
 include/linux/iommufd.h            |  7 +++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/iommu/iommufd/viommu_api.c b/drivers/iommu/iommufd/viommu_api.c
index 3772a5892a6c..82eb33e047cf 100644
--- a/drivers/iommu/iommufd/viommu_api.c
+++ b/drivers/iommu/iommufd/viommu_api.c
@@ -51,3 +51,17 @@ iommufd_viommu_to_parent_domain(struct iommufd_viommu *viommu)
 	return viommu->hwpt->common.domain;
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_viommu_to_parent_domain, IOMMUFD);
+
+/*
+ * Fetch the dev pointer in the vdev_id structure. Caller must make ensure the
+ * lifecycle of the vdev_id structure, likely by adding a driver-level lock to
+ * protect the passed-in vdev_id for any race against a potential unset_vdev_id
+ * callback.
+ */
+struct device *iommufd_vdev_id_to_dev(struct iommufd_vdev_id *vdev_id)
+{
+	if (!vdev_id || !vdev_id->viommu)
+		return NULL;
+	return vdev_id->idev->dev;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_vdev_id_to_dev, IOMMUFD);
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index c89583c7c792..88d6586a424f 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -99,6 +99,7 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
 				unsigned long iova, unsigned long length);
 int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
 		      void *data, size_t len, unsigned int flags);
+struct device *iommufd_vdev_id_to_dev(struct iommufd_vdev_id *vdev_id);
 int iommufd_vfio_compat_ioas_get_id(struct iommufd_ctx *ictx, u32 *out_ioas_id);
 int iommufd_vfio_compat_ioas_create(struct iommufd_ctx *ictx);
 int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx);
@@ -138,6 +139,12 @@ static inline int iommufd_access_rw(struct iommufd_access *access, unsigned long
 	return -EOPNOTSUPP;
 }
 
+static inline struct device *
+iommufd_vdev_id_to_dev(struct iommufd_vdev_id *vdev_id)
+{
+	return NULL;
+}
+
 static inline int iommufd_vfio_compat_ioas_create(struct iommufd_ctx *ictx)
 {
 	return -EOPNOTSUPP;
-- 
2.43.0