[PATCH v2 2/3] drm: shmem: Add drm_gem_shmem_map_offset() wrapper

[Steven Price]

Provide a wrapper for drm_gem_map_offset() for clients of shmem. This
wrapper provides the correct semantics for the drm_gem_shmem_mmap()
callback.

Signed-off-by: Steven Price <steven.price@xxxxxxx>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 20 ++++++++++++++++++++
 include/drm/drm_gem_shmem_helper.h     |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 1ee208c2c85e..9dbebc4897d1 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -400,6 +400,26 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
 
+/**
+ * drm_gem_map_offset - return the fake mmap offset for a gem object
+ * @file: drm file-private structure containing the gem object
+ * @dev: corresponding drm_device
+ * @handle: gem object handle
+ * @offset: return location for the fake mmap offset
+ *
+ * This provides an offset suitable for user space to return to the
+ * drm_gem_shmem_mmap() callback via an mmap() call.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_map_offset(struct drm_file *file, struct drm_device *dev,
+			     u32 handle, u64 *offset)
+{
+	return drm_gem_map_offset(file, dev, handle, offset);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_map_offset);
+
 static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 038b6d313447..4239ddaaaa4f 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -128,6 +128,8 @@ drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
 int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
 			      struct drm_mode_create_dumb *args);
 
+int drm_gem_shmem_map_offset(struct drm_file *file, struct drm_device *dev,
+			     u32 handle, u64 *offset);
 int drm_gem_shmem_mmap(struct file *filp, struct vm_area_struct *vma);
 
 extern const struct vm_operations_struct drm_gem_shmem_vm_ops;
-- 
2.20.1