linux-kernel - [PATCH] dmatest: properly handle duplicate DMA channels

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Date:	Thu, 18 Sep 2008 10:21:19 -0500
From:	Timur Tabi <timur@...escale.com>
To:	dan.j.williams@...el.com, haavard.skinnemoen@...el.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH] 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.

Signed-off-by: Timur Tabi <timur@...escale.com>
---
 drivers/dma/dmatest.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index a08d197..2689d90 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -321,10 +321,15 @@ static void dmatest_cleanup_channel(struct dmatest_chan *dtc)
 
 static enum dma_state_client dmatest_add_channel(struct dma_chan *chan)
 {
-	struct dmatest_chan	*dtc;
+	struct dmatest_chan	*dtc, *_dtc;
 	struct dmatest_thread	*thread;
 	unsigned int		i;
 
+	/* Have we already been told about this channel? */
+	list_for_each_entry_safe(dtc, _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);
-- 
1.5.5

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