dma-buf: cleanup dma_buf_export() to make it easily extensible

At present, dma_buf_export() takes a series of parameters, which
makes it difficult to add any new parameters for exporters, if required.

Make it simpler by moving all these parameters into a struct, and pass
the struct * as parameter to dma_buf_export().

While at it, unite dma_buf_export_named() with dma_buf_export(), and
change all callers accordingly.
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

Documentation/dma-buf-sharing.txt

@@ -49,25 +49,26 @@ The dma_buf buffer sharing API usage contains the following steps:
    The buffer exporter announces its wish to export a buffer. In this, it
    connects its own private buffer data, provides implementation for operations
    that can be performed on the exported dma_buf, and flags for the file
-   associated with this buffer.
+   associated with this buffer. All these fields are filled in struct
+   dma_buf_export_info, defined via the DEFINE_DMA_BUF_EXPORT_INFO macro.
 
    Interface:
-      struct dma_buf *dma_buf_export_named(void *priv, struct dma_buf_ops *ops,
-				     size_t size, int flags,
-				     const char *exp_name)
+      DEFINE_DMA_BUF_EXPORT_INFO(exp_info)
+      struct dma_buf *dma_buf_export(struct dma_buf_export_info *exp_info)
 
-   If this succeeds, dma_buf_export_named allocates a dma_buf structure, and
+   If this succeeds, dma_buf_export allocates a dma_buf structure, and
    returns a pointer to the same. It also associates an anonymous file with this
    buffer, so it can be exported. On failure to allocate the dma_buf object,
    it returns NULL.
 
-   'exp_name' is the name of exporter - to facilitate information while
-   debugging.
+   'exp_name' in struct dma_buf_export_info is the name of exporter - to
+   facilitate information while debugging. It is set to KBUILD_MODNAME by
+   default, so exporters don't have to provide a specific name, if they don't
+   wish to.
+
+   DEFINE_DMA_BUF_EXPORT_INFO macro defines the struct dma_buf_export_info,
+   zeroes it out and pre-populates exp_name in it.
 
-   Exporting modules which do not wish to provide any specific name may use the
-   helper define 'dma_buf_export()', with the same arguments as above, but
-   without the last argument; a KBUILD_MODNAME pre-processor directive will be
-   inserted in place of 'exp_name' instead.
 
 2. Userspace gets a handle to pass around to potential buffer-users
 

drivers/dma-buf/dma-buf.c

@@ -265,43 +265,40 @@ static inline int is_dma_buf_file(struct file *file)
 }
 
 /**
- * dma_buf_export_named - Creates a new dma_buf, and associates an anon file
+ * dma_buf_export - Creates a new dma_buf, and associates an anon file
  * with this buffer, so it can be exported.
  * Also connect the allocator specific data and ops to the buffer.
  * Additionally, provide a name string for exporter; useful in debugging.
  *
- * @priv:	[in]	Attach private data of allocator to this buffer
- * @ops:	[in]	Attach allocator-defined dma buf ops to the new buffer.
- * @size:	[in]	Size of the buffer
- * @flags:	[in]	mode flags for the file.
- * @exp_name:	[in]	name of the exporting module - useful for debugging.
- * @resv:	[in]	reservation-object, NULL to allocate default one.
+ * @exp_info:	[in]	holds all the export related information provided
+ *			by the exporter. see struct dma_buf_export_info
+ *			for further details.
  *
  * Returns, on success, a newly created dma_buf object, which wraps the
  * supplied private data and operations for dma_buf_ops. On either missing
  * ops, or error in allocating struct dma_buf, will return negative error.
  *
  */
-struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
-				size_t size, int flags, const char *exp_name,
-				struct reservation_object *resv)
+struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 {
 	struct dma_buf *dmabuf;
+	struct reservation_object *resv = exp_info->resv;
 	struct file *file;
 	size_t alloc_size = sizeof(struct dma_buf);
-	if (!resv)
+	if (!exp_info->resv)
 		alloc_size += sizeof(struct reservation_object);
 	else
 		/* prevent &dma_buf[1] == dma_buf->resv */
 		alloc_size += 1;
 
-	if (WARN_ON(!priv || !ops
-			  || !ops->map_dma_buf
-			  || !ops->unmap_dma_buf
-			  || !ops->release
-			  || !ops->kmap_atomic
-			  || !ops->kmap
-			  || !ops->mmap)) {
+	if (WARN_ON(!exp_info->priv
+			  || !exp_info->ops
+			  || !exp_info->ops->map_dma_buf
+			  || !exp_info->ops->unmap_dma_buf
+			  || !exp_info->ops->release
+			  || !exp_info->ops->kmap_atomic
+			  || !exp_info->ops->kmap
+			  || !exp_info->ops->mmap)) {
 		return ERR_PTR(-EINVAL);
 	}
 
@@ -309,10 +306,10 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
 	if (dmabuf == NULL)
 		return ERR_PTR(-ENOMEM);
 
-	dmabuf->priv = priv;
-	dmabuf->ops = ops;
-	dmabuf->size = size;
-	dmabuf->exp_name = exp_name;
+	dmabuf->priv = exp_info->priv;
+	dmabuf->ops = exp_info->ops;
+	dmabuf->size = exp_info->size;
+	dmabuf->exp_name = exp_info->exp_name;
 	init_waitqueue_head(&dmabuf->poll);
 	dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
 	dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
@@ -323,7 +320,8 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
 	}
 	dmabuf->resv = resv;
 
-	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
+	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf,
+					exp_info->flags);
 	if (IS_ERR(file)) {
 		kfree(dmabuf);
 		return ERR_CAST(file);
@@ -341,8 +339,7 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
 
 	return dmabuf;
 }
-EXPORT_SYMBOL_GPL(dma_buf_export_named);
-
+EXPORT_SYMBOL_GPL(dma_buf_export);
 
 /**
  * dma_buf_fd - returns a file descriptor for the given dma_buf

drivers/gpu/drm/armada/armada_gem.c

@@ -538,8 +538,14 @@ struct dma_buf *
 armada_gem_prime_export(struct drm_device *dev, struct drm_gem_object *obj,
 	int flags)
 {
-	return dma_buf_export(obj, &armada_gem_prime_dmabuf_ops, obj->size,
-			      O_RDWR, NULL);
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &armada_gem_prime_dmabuf_ops;
+	exp_info.size = obj->size;
+	exp_info.flags = O_RDWR;
+	exp_info.priv = obj;
+
+	return dma_buf_export(&exp_info);
 }
 
 struct drm_gem_object *

drivers/gpu/drm/drm_prime.c

@@ -339,13 +339,17 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops =  {
 struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
 				     struct drm_gem_object *obj, int flags)
 {
-	struct reservation_object *robj = NULL;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &drm_gem_prime_dmabuf_ops;
+	exp_info.size = obj->size;
+	exp_info.flags = flags;
+	exp_info.priv = obj;
 
 	if (dev->driver->gem_prime_res_obj)
-		robj = dev->driver->gem_prime_res_obj(obj);
+		exp_info.resv = dev->driver->gem_prime_res_obj(obj);
 
-	return dma_buf_export(obj, &drm_gem_prime_dmabuf_ops, obj->size,
-			      flags, robj);
+	return dma_buf_export(&exp_info);
 }
 EXPORT_SYMBOL(drm_gem_prime_export);
 

drivers/gpu/drm/exynos/exynos_drm_dmabuf.c

@@ -185,9 +185,14 @@ struct dma_buf *exynos_dmabuf_prime_export(struct drm_device *drm_dev,
 				struct drm_gem_object *obj, int flags)
 {
 	struct exynos_drm_gem_obj *exynos_gem_obj = to_exynos_gem_obj(obj);
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
 
-	return dma_buf_export(obj, &exynos_dmabuf_ops,
-				exynos_gem_obj->base.size, flags, NULL);
+	exp_info.ops = &exynos_dmabuf_ops;
+	exp_info.size = exynos_gem_obj->base.size;
+	exp_info.flags = flags;
+	exp_info.priv = obj;
+
+	return dma_buf_export(&exp_info);
 }
 
 struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,

drivers/gpu/drm/i915/i915_gem_dmabuf.c

@@ -230,6 +230,13 @@ struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 				      struct drm_gem_object *gem_obj, int flags)
 {
 	struct drm_i915_gem_object *obj = to_intel_bo(gem_obj);
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &i915_dmabuf_ops;
+	exp_info.size = gem_obj->size;
+	exp_info.flags = flags;
+	exp_info.priv = gem_obj;
+
 
 	if (obj->ops->dmabuf_export) {
 		int ret = obj->ops->dmabuf_export(obj);
@@ -237,8 +244,7 @@ struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 			return ERR_PTR(ret);
 	}
 
-	return dma_buf_export(gem_obj, &i915_dmabuf_ops, gem_obj->size, flags,
-			      NULL);
+	return dma_buf_export(&exp_info);
 }
 
 static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj)

drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c

@@ -171,7 +171,14 @@ static struct dma_buf_ops omap_dmabuf_ops = {
 struct dma_buf *omap_gem_prime_export(struct drm_device *dev,
 		struct drm_gem_object *obj, int flags)
 {
-	return dma_buf_export(obj, &omap_dmabuf_ops, obj->size, flags, NULL);
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &omap_dmabuf_ops;
+	exp_info.size = obj->size;
+	exp_info.flags = flags;
+	exp_info.priv = obj;
+
+	return dma_buf_export(&exp_info);
 }
 
 struct drm_gem_object *omap_gem_prime_import(struct drm_device *dev,

drivers/gpu/drm/tegra/gem.c

@@ -627,8 +627,14 @@ struct dma_buf *tegra_gem_prime_export(struct drm_device *drm,
 				       struct drm_gem_object *gem,
 				       int flags)
 {
-	return dma_buf_export(gem, &tegra_gem_prime_dmabuf_ops, gem->size,
-			      flags, NULL);
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &tegra_gem_prime_dmabuf_ops;
+	exp_info.size = gem->size;
+	exp_info.flags = flags;
+	exp_info.priv = gem;
+
+	return dma_buf_export(&exp_info);
 }
 
 struct drm_gem_object *tegra_gem_prime_import(struct drm_device *drm,

drivers/gpu/drm/ttm/ttm_object.c

@@ -683,6 +683,12 @@ int ttm_prime_handle_to_fd(struct ttm_object_file *tfile,
 
 	dma_buf = prime->dma_buf;
 	if (!dma_buf || !get_dma_buf_unless_doomed(dma_buf)) {
+		DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+		exp_info.ops = &tdev->ops;
+		exp_info.size = prime->size;
+		exp_info.flags = flags;
+		exp_info.priv = prime;
 
 		/*
 		 * Need to create a new dma_buf, with memory accounting.
@@ -694,8 +700,7 @@ int ttm_prime_handle_to_fd(struct ttm_object_file *tfile,
 			goto out_unref;
 		}
 
-		dma_buf = dma_buf_export(prime, &tdev->ops,
-					 prime->size, flags, NULL);
+		dma_buf = dma_buf_export(&exp_info);
 		if (IS_ERR(dma_buf)) {
 			ret = PTR_ERR(dma_buf);
 			ttm_mem_global_free(tdev->mem_glob,

drivers/gpu/drm/udl/udl_dmabuf.c

@@ -202,7 +202,14 @@ static struct dma_buf_ops udl_dmabuf_ops = {
 struct dma_buf *udl_gem_prime_export(struct drm_device *dev,
 				     struct drm_gem_object *obj, int flags)
 {
-	return dma_buf_export(obj, &udl_dmabuf_ops, obj->size, flags, NULL);
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &udl_dmabuf_ops;
+	exp_info.size = obj->size;
+	exp_info.flags = flags;
+	exp_info.priv = obj;
+
+	return dma_buf_export(&exp_info);
 }
 
 static int udl_prime_create(struct drm_device *dev,

drivers/media/v4l2-core/videobuf2-dma-contig.c

@@ -402,6 +402,12 @@ static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
 {
 	struct vb2_dc_buf *buf = buf_priv;
 	struct dma_buf *dbuf;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &vb2_dc_dmabuf_ops;
+	exp_info.size = buf->size;
+	exp_info.flags = flags;
+	exp_info.priv = buf;
 
 	if (!buf->sgt_base)
 		buf->sgt_base = vb2_dc_get_base_sgt(buf);
@@ -409,7 +415,7 @@ static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
 	if (WARN_ON(!buf->sgt_base))
 		return NULL;
 
-	dbuf = dma_buf_export(buf, &vb2_dc_dmabuf_ops, buf->size, flags, NULL);
+	dbuf = dma_buf_export(&exp_info);
 	if (IS_ERR(dbuf))
 		return NULL;
 

drivers/media/v4l2-core/videobuf2-dma-sg.c

@@ -583,11 +583,17 @@ static struct dma_buf *vb2_dma_sg_get_dmabuf(void *buf_priv, unsigned long flags
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct dma_buf *dbuf;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &vb2_dma_sg_dmabuf_ops;
+	exp_info.size = buf->size;
+	exp_info.flags = flags;
+	exp_info.priv = buf;
 
 	if (WARN_ON(!buf->dma_sgt))
 		return NULL;
 
-	dbuf = dma_buf_export(buf, &vb2_dma_sg_dmabuf_ops, buf->size, flags, NULL);
+	dbuf = dma_buf_export(&exp_info);
 	if (IS_ERR(dbuf))
 		return NULL;
 

drivers/media/v4l2-core/videobuf2-vmalloc.c

@@ -368,11 +368,17 @@ static struct dma_buf *vb2_vmalloc_get_dmabuf(void *buf_priv, unsigned long flag
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;
 	struct dma_buf *dbuf;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &vb2_vmalloc_dmabuf_ops;
+	exp_info.size = buf->size;
+	exp_info.flags = flags;
+	exp_info.priv = buf;
 
 	if (WARN_ON(!buf->vaddr))
 		return NULL;
 
-	dbuf = dma_buf_export(buf, &vb2_vmalloc_dmabuf_ops, buf->size, flags, NULL);
+	dbuf = dma_buf_export(&exp_info);
 	if (IS_ERR(dbuf))
 		return NULL;
 

drivers/staging/android/ion/ion.c

@@ -1106,6 +1106,12 @@ struct dma_buf *ion_share_dma_buf(struct ion_client *client,
 	struct ion_buffer *buffer;
 	struct dma_buf *dmabuf;
 	bool valid_handle;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &dma_buf_ops;
+	exp_info.size = buffer->size;
+	exp_info.flags = O_RDWR;
+	exp_info.priv = buffer;
 
 	mutex_lock(&client->lock);
 	valid_handle = ion_handle_validate(client, handle);
@@ -1118,8 +1124,7 @@ struct dma_buf *ion_share_dma_buf(struct ion_client *client,
 	ion_buffer_get(buffer);
 	mutex_unlock(&client->lock);
 
-	dmabuf = dma_buf_export(buffer, &dma_buf_ops, buffer->size, O_RDWR,
-				NULL);
+	dmabuf = dma_buf_export(&exp_info);
 	if (IS_ERR(dmabuf)) {
 		ion_buffer_put(buffer);
 		return dmabuf;

include/linux/dma-buf.h

@@ -162,6 +162,33 @@ struct dma_buf_attachment {
 	void *priv;
 };
 
+/**
+ * struct dma_buf_export_info - holds information needed to export a dma_buf
+ * @exp_name:	name of the exporting module - useful for debugging.
+ * @ops:	Attach allocator-defined dma buf ops to the new buffer
+ * @size:	Size of the buffer
+ * @flags:	mode flags for the file
+ * @resv:	reservation-object, NULL to allocate default one
+ * @priv:	Attach private data of allocator to this buffer
+ *
+ * This structure holds the information required to export the buffer. Used
+ * with dma_buf_export() only.
+ */
+struct dma_buf_export_info {
+	const char *exp_name;
+	const struct dma_buf_ops *ops;
+	size_t size;
+	int flags;
+	struct reservation_object *resv;
+	void *priv;
+};
+
+/**
+ * helper macro for exporters; zeros and fills in most common values
+ */
+#define DEFINE_DMA_BUF_EXPORT_INFO(a)	\
+	struct dma_buf_export_info a = { .exp_name = KBUILD_MODNAME }
+
 /**
  * get_dma_buf - convenience wrapper for get_file.
  * @dmabuf:	[in]	pointer to dma_buf
@@ -181,12 +208,7 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 void dma_buf_detach(struct dma_buf *dmabuf,
 				struct dma_buf_attachment *dmabuf_attach);
 
-struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
-			       size_t size, int flags, const char *,
-			       struct reservation_object *);
-
-#define dma_buf_export(priv, ops, size, flags, resv)	\
-	dma_buf_export_named(priv, ops, size, flags, KBUILD_MODNAME, resv)
+struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
 
 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
 struct dma_buf *dma_buf_get(int fd);