[PATCH 1/6] drm: Add helper to check exporting driver of a DMA-buf

[Felix Kuehling <Felix.Kuehling@xxxxxxx>]

This allows drivers to check if a DMA-buf contains a GEM object and
whether it comes from the same driver. It may be from the same or a
different device.

Signed-off-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
---
 drivers/gpu/drm/drm_prime.c | 24 ++++++++++++++++++++++++
 include/drm/drmP.h          |  2 ++
 2 files changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 25aa455..a50baec 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -594,6 +594,30 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
 EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);
 
 /**
+ * drm_gem_prime_dmabuf_is_from_driver - check exporting driver of a dma-buf
+ * @dma_buf: dma-buf object to check
+ * @driver: driver that is the expected exporter of the dma-buf
+ *
+ * Returns true if @driver exported @dma_buf. Returns false if
+ * @dma_buf was exported by a different driver.
+ */
+bool drm_gem_prime_dmabuf_is_from_driver(const struct dma_buf *dma_buf,
+					 const struct drm_driver *driver)
+{
+	struct drm_gem_object *obj;
+
+	if (dma_buf->ops != &drm_gem_prime_dmabuf_ops)
+		return false;
+
+	obj = dma_buf->priv;
+	if (obj->dev->driver != driver)
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL(drm_gem_prime_dmabuf_is_from_driver);
+
+/**
  * drm_gem_prime_import - helper library implementation of the import callback
  * @dev: drm_device to import into
  * @dma_buf: dma-buf object to import
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 6105c05..052f747 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -767,6 +767,8 @@ extern struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
 extern int drm_gem_prime_handle_to_fd(struct drm_device *dev,
 		struct drm_file *file_priv, uint32_t handle, uint32_t flags,
 		int *prime_fd);
+extern bool drm_gem_prime_dmabuf_is_from_driver(const struct dma_buf *dma_buf,
+		const struct drm_driver *driver);
 extern struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 		struct dma_buf *dma_buf);
 extern int drm_gem_prime_fd_to_handle(struct drm_device *dev,
-- 
1.9.1

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