Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma

[firefly-linux-kernel-4.4.55.git] / drivers / dma / dmaengine.c

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index eee16b01fa8951a7634408a6e65eaceacf5e9705..9162ac80c18f303ac9a509eb97298eba33d4753b 100644 (file)
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -509,7 +509,33 @@ static struct dma_chan *private_candidate(const dma_cap_mask_t *mask,
 }
 
 /**
- * dma_request_channel - try to allocate an exclusive channel
+ * dma_request_slave_channel - try to get specific channel exclusively
+ * @chan: target channel
+ */
+struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
+{
+       int err = -EBUSY;
+
+       /* lock against __dma_request_channel */
+       mutex_lock(&dma_list_mutex);
+
+       if (chan->client_count == 0) {
+               err = dma_chan_get(chan);
+               if (err)
+                       pr_debug("%s: failed to get %s: (%d)\n",
+                               __func__, dma_chan_name(chan), err);
+       } else
+               chan = NULL;
+
+       mutex_unlock(&dma_list_mutex);
+
+
+       return chan;
+}
+EXPORT_SYMBOL_GPL(dma_get_slave_channel);
+
+/**
+ * __dma_request_channel - try to allocate an exclusive channel
  * @mask: capabilities that the channel must satisfy
  * @fn: optional callback to disposition available channels
  * @fn_param: opaque parameter to pass to dma_filter_fn