acpi-dma: convert to return error code when asked for channel

Currently acpi_dma_request_slave_chan_by_index() and
acpi_dma_request_slave_chan_by_name() return only requested channel or NULL.
This patch converts them to return appropriate error code instead of NULL in
case of unsuccessfull request.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/acpi-dma.c

@@ -13,6 +13,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/err.h>
 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
@@ -343,7 +344,7 @@ static int acpi_dma_parse_fixed_dma(struct acpi_resource *res, void *data)
  * @index:	index of FixedDMA descriptor for @dev
  *
  * Return:
- * Pointer to appropriate dma channel on success or NULL on error.
+ * Pointer to appropriate dma channel on success or an error pointer.
  */
 struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
 		size_t index)
@@ -358,10 +359,10 @@ struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
 
 	/* Check if the device was enumerated by ACPI */
 	if (!dev || !ACPI_HANDLE(dev))
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	if (acpi_bus_get_device(ACPI_HANDLE(dev), &adev))
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	memset(&pdata, 0, sizeof(pdata));
 	pdata.index = index;
@@ -376,7 +377,7 @@ struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
 	acpi_dev_free_resource_list(&resource_list);
 
 	if (dma_spec->slave_id < 0 || dma_spec->chan_id < 0)
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	mutex_lock(&acpi_dma_lock);
 
@@ -399,7 +400,7 @@ struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
 	}
 
 	mutex_unlock(&acpi_dma_lock);
-	return chan;
+	return chan ? chan : ERR_PTR(-EPROBE_DEFER);
 }
 EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);
 
@@ -413,7 +414,7 @@ EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);
  * the first FixedDMA descriptor is TX and second is RX.
  *
  * Return:
- * Pointer to appropriate dma channel on success or NULL on error.
+ * Pointer to appropriate dma channel on success or an error pointer.
  */
 struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
 		const char *name)
@@ -425,7 +426,7 @@ struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
 	else if (!strcmp(name, "rx"))
 		index = 1;
 	else
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	return acpi_dma_request_slave_chan_by_index(dev, index);
 }

drivers/dma/dmaengine.c

@@ -627,18 +627,13 @@ EXPORT_SYMBOL_GPL(__dma_request_channel);
 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)) {
-		chan = acpi_dma_request_slave_chan_by_name(dev, name);
-		if (chan)
-			return chan;
-	}
+	if (ACPI_HANDLE(dev))
+		return acpi_dma_request_slave_chan_by_name(dev, name);
 
 	return ERR_PTR(-ENODEV);
 }

include/linux/acpi_dma.h

@@ -16,6 +16,7 @@
 
 #include <linux/list.h>
 #include <linux/device.h>
+#include <linux/err.h>
 #include <linux/dmaengine.h>
 
 /**
@@ -103,12 +104,12 @@ static inline void devm_acpi_dma_controller_free(struct device *dev)
 static inline struct dma_chan *acpi_dma_request_slave_chan_by_index(
 		struct device *dev, size_t index)
 {
-	return NULL;
+	return ERR_PTR(-ENODEV);
 }
 static inline struct dma_chan *acpi_dma_request_slave_chan_by_name(
 		struct device *dev, const char *name)
 {
-	return NULL;
+	return ERR_PTR(-ENODEV);
 }
 
 #define acpi_dma_simple_xlate	NULL