dw_dmac: introduce to_dw_desc() macro

The to_dw_desc() macro helps to retrieve the dw_desc node from the
corresponding list_head structure.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/dw_dmac.c

@@ -93,7 +93,7 @@ static struct device *chan2parent(struct dma_chan *chan)
 
 static struct dw_desc *dwc_first_active(struct dw_dma_chan *dwc)
 {
-	return list_entry(dwc->active_list.next, struct dw_desc, desc_node);
+	return to_dw_desc(dwc->active_list.next);
 }
 
 static struct dw_desc *dwc_desc_get(struct dw_dma_chan *dwc)
@@ -600,9 +600,7 @@ static void dw_dma_tasklet(unsigned long data)
 			if (test_bit(DW_DMA_IS_SOFT_LLP, &dwc->flags)) {
 				if (dwc->tx_node_active != dwc->tx_list) {
 					struct dw_desc *desc =
-						list_entry(dwc->tx_node_active,
-							   struct dw_desc,
-							   desc_node);
+						to_dw_desc(dwc->tx_node_active);
 
 					dma_writel(dw, CLEAR.XFER, dwc->mask);
 

drivers/dma/dw_dmac_regs.h

@@ -299,6 +299,8 @@ struct dw_desc {
 	size_t				len;
 };
 
+#define to_dw_desc(h)	list_entry(h, struct dw_desc, desc_node)
+
 static inline struct dw_desc *
 txd_to_dw_desc(struct dma_async_tx_descriptor *txd)
 {