iio: buffer-dma: add iio_dmaengine_buffer_setup()

This brings the DMA buffer API more in line with what we have in the
triggered buffer. There's no need of having both
devm_iio_dmaengine_buffer_setup() and devm_iio_dmaengine_buffer_alloc().
Hence we introduce the new iio_dmaengine_buffer_setup() that together
with devm_iio_dmaengine_buffer_setup() should be all we need.

Note that as part of this change iio_dmaengine_buffer_alloc() is again
static and the axi-adc was updated accordingly.
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-1-5ca45b4de294@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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

@@ -124,26 +124,12 @@ static struct iio_buffer *axi_adc_request_buffer(struct iio_backend *back,
 						 struct iio_dev *indio_dev)
 {
 	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
-	struct iio_buffer *buffer;
 	const char *dma_name;
-	int ret;
 
 	if (device_property_read_string(st->dev, "dma-names", &dma_name))
 		dma_name = "rx";
 
-	buffer = iio_dmaengine_buffer_alloc(st->dev, dma_name);
-	if (IS_ERR(buffer)) {
-		dev_err(st->dev, "Could not get DMA buffer, %ld\n",
-			PTR_ERR(buffer));
-		return ERR_CAST(buffer);
-	}
-
-	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
-	ret = iio_device_attach_buffer(indio_dev, buffer);
-	if (ret)
-		return ERR_PTR(ret);
-
-	return buffer;
+	return iio_dmaengine_buffer_setup(st->dev, indio_dev, dma_name);
 }
 
 static void axi_adc_free_buffer(struct iio_backend *back,

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

@@ -159,7 +159,7 @@ static const struct iio_dev_attr *iio_dmaengine_buffer_attrs[] = {
  * Once done using the buffer iio_dmaengine_buffer_free() should be used to
  * release it.
  */
-struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
+static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 	const char *channel)
 {
 	struct dmaengine_buffer *dmaengine_buffer;
@@ -210,7 +210,6 @@ struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 	kfree(dmaengine_buffer);
 	return ERR_PTR(ret);
 }
-EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_alloc, IIO_DMAENGINE_BUFFER);
 
 /**
  * iio_dmaengine_buffer_free() - Free dmaengine buffer
@@ -230,39 +229,33 @@ void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
 }
 EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_free, IIO_DMAENGINE_BUFFER);
 
-static void __devm_iio_dmaengine_buffer_free(void *buffer)
-{
-	iio_dmaengine_buffer_free(buffer);
-}
-
-/**
- * devm_iio_dmaengine_buffer_alloc() - Resource-managed iio_dmaengine_buffer_alloc()
- * @dev: Parent device for the buffer
- * @channel: DMA channel name, typically "rx".
- *
- * This allocates a new IIO buffer which internally uses the DMAengine framework
- * to perform its transfers. The parent device will be used to request the DMA
- * channel.
- *
- * The buffer will be automatically de-allocated once the device gets destroyed.
- */
-static struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
-	const char *channel)
+struct iio_buffer *iio_dmaengine_buffer_setup(struct device *dev,
+					      struct iio_dev *indio_dev,
+					      const char *channel)
 {
 	struct iio_buffer *buffer;
 	int ret;
 
 	buffer = iio_dmaengine_buffer_alloc(dev, channel);
 	if (IS_ERR(buffer))
-		return buffer;
+		return ERR_CAST(buffer);
+
+	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
 
-	ret = devm_add_action_or_reset(dev, __devm_iio_dmaengine_buffer_free,
-				       buffer);
-	if (ret)
+	ret = iio_device_attach_buffer(indio_dev, buffer);
+	if (ret) {
+		iio_dmaengine_buffer_free(buffer);
 		return ERR_PTR(ret);
+	}
 
 	return buffer;
 }
+EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_setup, IIO_DMAENGINE_BUFFER);
+
+static void __devm_iio_dmaengine_buffer_free(void *buffer)
+{
+	iio_dmaengine_buffer_free(buffer);
+}
 
 /**
  * devm_iio_dmaengine_buffer_setup() - Setup a DMA buffer for an IIO device
@@ -281,13 +274,12 @@ int devm_iio_dmaengine_buffer_setup(struct device *dev,
 {
 	struct iio_buffer *buffer;
 
-	buffer = devm_iio_dmaengine_buffer_alloc(dev, channel);
+	buffer = iio_dmaengine_buffer_setup(dev, indio_dev, channel);
 	if (IS_ERR(buffer))
 		return PTR_ERR(buffer);
 
-	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
-
-	return iio_device_attach_buffer(indio_dev, buffer);
+	return devm_add_action_or_reset(dev, __devm_iio_dmaengine_buffer_free,
+					buffer);
 }
 EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup, IIO_DMAENGINE_BUFFER);
 

include/linux/iio/buffer-dmaengine.h

@@ -10,9 +10,10 @@
 struct iio_dev;
 struct device;
 
-struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
-					      const char *channel);
 void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
+struct iio_buffer *iio_dmaengine_buffer_setup(struct device *dev,
+					      struct iio_dev *indio_dev,
+					      const char *channel);
 int devm_iio_dmaengine_buffer_setup(struct device *dev,
 				    struct iio_dev *indio_dev,
 				    const char *channel);