dmaengine: track the number of clients using a channel

Haavard's dma-slave interface would like to test for exclusive access to a
channel.  The standard channel refcounting is not sufficient in that it
tracks more than just client references, it is also inaccurate as reference
counts are percpu until the channel is removed.

This change also enables a future fix to deallocate resources when a client
declines to use a capable channel.

Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index d08a5c5eb928..6432b8343220 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -139,6 +139,7 @@ struct dma_chan_percpu {
  * @rcu: the DMA channel's RCU head
  * @device_node: used to add this to the device chan list
  * @local: per-cpu pointer to a struct dma_chan_percpu
+ * @client-count: how many clients are using this channel
  */
 struct dma_chan {
         struct dma_device *device;
@@ -154,6 +155,7 @@ struct dma_chan {
 
         struct list_head device_node;
         struct dma_chan_percpu *local;
+        int client_count;
 };
 
 #define to_dma_chan(p) container_of(p, struct dma_chan, dev)