[PATCH 1/3] udmabuf: Keep track current device mappings

[Andrew Davis <afd@xxxxxx>]

When a device attaches to and maps our buffer we need to keep track
of this mapping/device. This is needed for synchronization with these
devices when beginning and ending CPU access for instance. Add a list
that tracks device mappings as part of {map,unmap}_udmabuf().

Signed-off-by: Andrew Davis <afd@xxxxxx>
---
 drivers/dma-buf/udmabuf.c | 43 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index c406459996489..3a23f0a7d112a 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -28,6 +28,14 @@ struct udmabuf {
 	struct page **pages;
 	struct sg_table *sg;
 	struct miscdevice *device;
+	struct list_head attachments;
+	struct mutex lock;
+};
+
+struct udmabuf_attachment {
+	struct device *dev;
+	struct sg_table *table;
+	struct list_head list;
 };
 
 static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
@@ -120,14 +128,42 @@ static void put_sg_table(struct device *dev, struct sg_table *sg,
 static struct sg_table *map_udmabuf(struct dma_buf_attachment *at,
 				    enum dma_data_direction direction)
 {
-	return get_sg_table(at->dev, at->dmabuf, direction);
+	struct udmabuf *ubuf = at->dmabuf->priv;
+	struct udmabuf_attachment *a;
+
+	a = kzalloc(sizeof(*a), GFP_KERNEL);
+	if (!a)
+		return ERR_PTR(-ENOMEM);
+
+	a->table = get_sg_table(at->dev, at->dmabuf, direction);
+	if (IS_ERR(a->table)) {
+		kfree(a);
+		return a->table;
+	}
+
+	a->dev = at->dev;
+
+	mutex_lock(&ubuf->lock);
+	list_add(&a->list, &ubuf->attachments);
+	mutex_unlock(&ubuf->lock);
+
+	return a->table;
 }
 
 static void unmap_udmabuf(struct dma_buf_attachment *at,
 			  struct sg_table *sg,
 			  enum dma_data_direction direction)
 {
-	return put_sg_table(at->dev, sg, direction);
+	struct udmabuf_attachment *a = at->priv;
+	struct udmabuf *ubuf = at->dmabuf->priv;
+
+	mutex_lock(&ubuf->lock);
+	list_del(&a->list);
+	mutex_unlock(&ubuf->lock);
+
+	put_sg_table(at->dev, sg, direction);
+
+	kfree(a);
 }
 
 static void release_udmabuf(struct dma_buf *buf)
@@ -263,6 +299,9 @@ static long udmabuf_create(struct miscdevice *device,
 		memfd = NULL;
 	}
 
+	INIT_LIST_HEAD(&ubuf->attachments);
+	mutex_init(&ubuf->lock);
+
 	exp_info.ops  = &udmabuf_ops;
 	exp_info.size = ubuf->pagecount << PAGE_SHIFT;
 	exp_info.priv = ubuf;
-- 
2.39.2