dmaengine: virt-dma: vchan_find_desc()

Add a function to find a descriptor within the depths of the
virtualized DMA channel support.  Needed for tx_status functionality.

Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 14 insertions, 1 deletions

diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
index bd85b052b481..a8054fc40cef 100644
--- a/drivers/dma/virt-dma.c
+++ b/drivers/dma/virt-dma.c
@@ -39,6 +39,19 @@ dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx)
 }
 EXPORT_SYMBOL_GPL(vchan_tx_submit);
 
+struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
+        dma_cookie_t cookie)
+{
+        struct virt_dma_desc *vd;
+
+        list_for_each_entry(vd, &vc->desc_issued, node)
+                if (vd->tx.cookie == cookie)
+                        return vd;
+
+        return NULL;
+}
+EXPORT_SYMBOL_GPL(vchan_find_desc);
+
 /*
  * This tasklet handles the completion of a DMA descriptor by
  * calling its callback and freeing it.
diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
index 825bb9623175..44ec57e7e419 100644
--- a/drivers/dma/virt-dma.h
+++ b/drivers/dma/virt-dma.h
@@ -40,8 +40,8 @@ static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
 }
 
 void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head);
-
 void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev);
+struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *, dma_cookie_t);
 
 /**
  * vchan_tx_prep - prepare a descriptor