Merge branch 'topic/defer_probe' of git://git.infradead.org/users/vkoul/slave-dma into asoc-dma

The following branch/patch is a dependency for my "ASoC: dmaengine:
support deferred probe for DMA channels". If you could pull the branch
below into your topic/dma, then merge my ASoC patch, that would be
great. I would then like to merge your topic/dma into the Tegra tree as
a baseline for the Tegra conversion to the standard DMA DT bindings.

Vinod has confirmed this his topic/defer_probe branch is stable, and
won't be rebased:

https://lkml.org/lkml/2013/12/10/463

drivers/dma/dmaengine.c

@@ -540,6 +540,8 @@ EXPORT_SYMBOL_GPL(dma_get_slave_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
+ *
+ * Returns pointer to appropriate DMA channel on success or NULL.
  */
 struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
 				       dma_filter_fn fn, void *fn_param)
@@ -591,18 +593,43 @@ EXPORT_SYMBOL_GPL(__dma_request_channel);
  * dma_request_slave_channel - try to allocate an exclusive slave channel
  * @dev:	pointer to client device structure
  * @name:	slave channel name
+ *
+ * Returns pointer to appropriate DMA channel on success or an error pointer.
  */
-struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name)
+struct dma_chan *dma_request_slave_channel_reason(struct device *dev,
+						  const char *name)
 {
+	struct dma_chan *chan;
+
 	/* If device-tree is present get slave info from here */
 	if (dev->of_node)
 		return of_dma_request_slave_channel(dev->of_node, name);
 
 	/* If device was enumerated by ACPI get slave info from here */
-	if (ACPI_HANDLE(dev))
-		return acpi_dma_request_slave_chan_by_name(dev, name);
+	if (ACPI_HANDLE(dev)) {
+		chan = acpi_dma_request_slave_chan_by_name(dev, name);
+		if (chan)
+			return chan;
+	}
 
-	return NULL;
+	return ERR_PTR(-ENODEV);
+}
+EXPORT_SYMBOL_GPL(dma_request_slave_channel_reason);
+
+/**
+ * dma_request_slave_channel - try to allocate an exclusive slave channel
+ * @dev:	pointer to client device structure
+ * @name:	slave channel name
+ *
+ * Returns pointer to appropriate DMA channel on success or NULL.
+ */
+struct dma_chan *dma_request_slave_channel(struct device *dev,
+					   const char *name)
+{
+	struct dma_chan *ch = dma_request_slave_channel_reason(dev, name);
+	if (IS_ERR(ch))
+		return NULL;
+	return ch;
 }
 EXPORT_SYMBOL_GPL(dma_request_slave_channel);
 

drivers/dma/of-dma.c

@@ -143,7 +143,7 @@ static int of_dma_match_channel(struct device_node *np, const char *name,
  * @np:		device node to get DMA request from
  * @name:	name of desired channel
  *
- * Returns pointer to appropriate dma channel on success or NULL on error.
+ * Returns pointer to appropriate DMA channel on success or an error pointer.
  */
 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 					      const char *name)
@@ -152,17 +152,18 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 	struct of_dma		*ofdma;
 	struct dma_chan		*chan;
 	int			count, i;
+	int			ret_no_channel = -ENODEV;
 
 	if (!np || !name) {
 		pr_err("%s: not enough information provided\n", __func__);
-		return NULL;
+		return ERR_PTR(-ENODEV);
 	}
 
 	count = of_property_count_strings(np, "dma-names");
 	if (count < 0) {
 		pr_err("%s: dma-names property of node '%s' missing or empty\n",
 			__func__, np->full_name);
-		return NULL;
+		return ERR_PTR(-ENODEV);
 	}
 
 	for (i = 0; i < count; i++) {
@@ -172,10 +173,12 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 		mutex_lock(&of_dma_lock);
 		ofdma = of_dma_find_controller(&dma_spec);
 
-		if (ofdma)
+		if (ofdma) {
 			chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
-		else
+		} else {
+			ret_no_channel = -EPROBE_DEFER;
 			chan = NULL;
+		}
 
 		mutex_unlock(&of_dma_lock);
 
@@ -185,7 +188,7 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 			return chan;
 	}
 
-	return NULL;
+	return ERR_PTR(ret_no_channel);
 }
 
 /**

include/linux/dmaengine.h

@@ -22,6 +22,7 @@
 #define LINUX_DMAENGINE_H
 
 #include <linux/device.h>
+#include <linux/err.h>
 #include <linux/uio.h>
 #include <linux/bug.h>
 #include <linux/scatterlist.h>
@@ -1040,6 +1041,8 @@ enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
 void dma_issue_pending_all(void);
 struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
 					dma_filter_fn fn, void *fn_param);
+struct dma_chan *dma_request_slave_channel_reason(struct device *dev,
+						  const char *name);
 struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name);
 void dma_release_channel(struct dma_chan *chan);
 #else
@@ -1063,6 +1066,11 @@ static inline struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
 {
 	return NULL;
 }
+static inline struct dma_chan *dma_request_slave_channel_reason(
+					struct device *dev, const char *name)
+{
+	return ERR_PTR(-ENODEV);
+}
 static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
 							 const char *name)
 {