dmatest: properly handle duplicate DMA channels

Update the the dmatest driver so that it handles duplicate DMA channels
properly.

When a DMA client is notified of an available DMA channel, it must check if it
has already allocated resources for that channel.  If so, it should return
DMA_DUP.  This can happen, for example, if a DMA driver calls
dma_async_device_register() more than once.

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

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index a08d19704743..422500c6c163 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -325,6 +325,11 @@ static enum dma_state_client dmatest_add_channel(struct dma_chan *chan)
         struct dmatest_thread   *thread;
         unsigned int            i;
 
+        /* Have we already been told about this channel? */
+        list_for_each_entry(dtc, &dmatest_channels, node)
+                if (dtc->chan == chan)
+                        return DMA_DUP;
+
         dtc = kmalloc(sizeof(struct dmatest_chan), GFP_ATOMIC);
         if (!dtc) {
                 pr_warning("dmatest: No memory for %s\n", chan->dev.bus_id);