dmaengine: add interface of dma_get_slave_channel
Suggested by Arnd, add dma_get_slave_channel interface
Dma host driver could get specific channel specificied by request line, rather than filter.
host example:
static struct dma_chan *xx_of_dma_simple_xlate(struct of_phandle_args *dma_spec,
struct of_dma *ofdma)
{
struct xx_dma_dev *d = ofdma->of_dma_data;
unsigned int request = dma_spec->args[0];
if (request > d->dma_requests)
return NULL;
return dma_get_slave_channel(&(d->chans[request].vc.chan));
}
probe:
of_dma_controller_register((&op->dev)->of_node, xx_of_dma_simple_xlate, d);
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 9e56745..5932ab1 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -504,6 +504,32 @@
}
/**
+ * dma_request_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);
+ else
+ chan = NULL;
+
+ mutex_unlock(&dma_list_mutex);
+
+ if (err)
+ pr_debug("%s: failed to get %s: (%d)\n",
+ __func__, dma_chan_name(chan), err);
+
+ 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