iio: buffer-dma,adi-axi-adc: introduce devm_iio_dmaengine_buffer_setup()

This change does a conversion of the devm_iio_dmaengine_buffer_alloc() to
devm_iio_dmaengine_buffer_setup(). This will allocate an IIO DMA buffer and
attach it to the IIO device, similar to devm_iio_triggered_buffer_setup()
(though the underlying code is different, the final logic is the same).

Since the only user of the devm_iio_dmaengine_buffer_alloc() was the
adi-axi-adc driver, this change does the replacement in a single go in the
driver.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-7-alexandru.ardelean@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/driver-api/driver-model/devres.rst

@@ -285,6 +285,7 @@ I2C
 IIO
   devm_iio_device_alloc()
   devm_iio_device_register()
+  devm_iio_dmaengine_buffer_setup()
   devm_iio_kfifo_buffer_setup()
   devm_iio_triggered_buffer_setup()
   devm_iio_trigger_alloc()

drivers/iio/adc/adi-axi-adc.c

@@ -104,7 +104,6 @@ static unsigned int adi_axi_adc_read(struct adi_axi_adc_state *st,
 static int adi_axi_adc_config_dma_buffer(struct device *dev,
 					 struct iio_dev *indio_dev)
 {
-	struct iio_buffer *buffer;
 	const char *dma_name;
 
 	if (!device_property_present(dev, "dmas"))
@@ -113,15 +112,8 @@ static int adi_axi_adc_config_dma_buffer(struct device *dev,
 	if (device_property_read_string(dev, "dma-names", &dma_name))
 		dma_name = "rx";
 
-	buffer = devm_iio_dmaengine_buffer_alloc(indio_dev->dev.parent,
-						 dma_name);
-	if (IS_ERR(buffer))
-		return PTR_ERR(buffer);
-
-	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
-	iio_device_attach_buffer(indio_dev, buffer);
-
-	return 0;
+	return devm_iio_dmaengine_buffer_setup(indio_dev->dev.parent,
+					       indio_dev, dma_name);
 }
 
 static int adi_axi_adc_read_raw(struct iio_dev *indio_dev,

drivers/iio/buffer/industrialio-buffer-dmaengine.c

@@ -244,7 +244,7 @@ static void __devm_iio_dmaengine_buffer_free(struct device *dev, void *res)
  *
  * The buffer will be automatically de-allocated once the device gets destroyed.
  */
-struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
+static struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
 	const char *channel)
 {
 	struct iio_buffer **bufferp, *buffer;
@@ -265,7 +265,36 @@ struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
 
 	return buffer;
 }
-EXPORT_SYMBOL_GPL(devm_iio_dmaengine_buffer_alloc);
+
+/**
+ * devm_iio_dmaengine_buffer_setup() - Setup a DMA buffer for an IIO device
+ * @dev: Parent device for the buffer
+ * @indio_dev: IIO device to which to attach this buffer.
+ * @channel: DMA channel name, typically "rx".
+ *
+ * This allocates a new IIO buffer with devm_iio_dmaengine_buffer_alloc()
+ * and attaches it to an IIO device with iio_device_attach_buffer().
+ * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of the
+ * IIO device.
+ */
+int devm_iio_dmaengine_buffer_setup(struct device *dev,
+				    struct iio_dev *indio_dev,
+				    const char *channel)
+{
+	struct iio_buffer *buffer;
+
+	buffer = devm_iio_dmaengine_buffer_alloc(indio_dev->dev.parent,
+						 channel);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_iio_dmaengine_buffer_setup);
 
 MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
 MODULE_DESCRIPTION("DMA buffer for the IIO framework");

include/linux/iio/buffer-dmaengine.h

@@ -7,10 +7,11 @@
 #ifndef __IIO_DMAENGINE_H__
 #define __IIO_DMAENGINE_H__
 
-struct iio_buffer;
+struct iio_dev;
 struct device;
 
-struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
-						   const char *channel);
+int devm_iio_dmaengine_buffer_setup(struct device *dev,
+				    struct iio_dev *indio_dev,
+				    const char *channel);
 
 #endif