net: devmem: fix DMA direction on unmapping

Looks like we always unmap the DMA_BUF with DMA_FROM_DEVICE direction.
While at it unexport __net_devmem_dmabuf_binding_free(), it's internal.

Found by code inspection.

Fixes: bd61848 ("net: devmem: Implement TX path")
Acked-by: Stanislav Fomichev <[email protected]>
Reviewed-by: Mina Almasry <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

net/core/devmem.c

@@ -70,14 +70,13 @@ void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
 		gen_pool_destroy(binding->chunk_pool);
 
 	dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
-					  DMA_FROM_DEVICE);
+					  binding->direction);
 	dma_buf_detach(binding->dmabuf, binding->attachment);
 	dma_buf_put(binding->dmabuf);
 	xa_destroy(&binding->bound_rxqs);
 	kvfree(binding->tx_vec);
 	kfree(binding);
 }
-EXPORT_SYMBOL(__net_devmem_dmabuf_binding_free);
 
 struct net_iov *
 net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
@@ -208,6 +207,7 @@ net_devmem_bind_dmabuf(struct net_device *dev,
 	mutex_init(&binding->lock);
 
 	binding->dmabuf = dmabuf;
+	binding->direction = direction;
 
 	binding->attachment = dma_buf_attach(binding->dmabuf, dev->dev.parent);
 	if (IS_ERR(binding->attachment)) {
@@ -312,7 +312,7 @@ net_devmem_bind_dmabuf(struct net_device *dev,
 	kvfree(binding->tx_vec);
 err_unmap:
 	dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
-					  DMA_FROM_DEVICE);
+					  direction);
 err_detach:
 	dma_buf_detach(dmabuf, binding->attachment);
 err_free_binding:

net/core/devmem.h

@@ -56,6 +56,9 @@ struct net_devmem_dmabuf_binding {
 	 */
 	u32 id;
 
+	/* DMA direction, FROM_DEVICE for Rx binding, TO_DEVICE for Tx. */
+	enum dma_data_direction direction;
+
 	/* Array of net_iov pointers for this binding, sorted by virtual
 	 * address. This array is convenient to map the virtual addresses to
 	 * net_iovs in the TX path.
@@ -165,10 +168,6 @@ static inline void net_devmem_put_net_iov(struct net_iov *niov)
 {
 }
 
-static inline void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
-{
-}
-
 static inline struct net_devmem_dmabuf_binding *
 net_devmem_bind_dmabuf(struct net_device *dev,
 		       enum dma_data_direction direction,