Add a new devm_iio_dmaengine_buffer_setup_ext2() function to handle
cases where the DMA channel is managed by the caller rather than being
requested and released by the iio_dmaengine module.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---

v5 changes: none

v4 changes:
* This replaces "iio: buffer-dmaengine: generalize requesting DMA channel"
---
 drivers/iio/buffer/industrialio-buffer-dmaengine.c | 107 +++++++++++++++------
 include/linux/iio/buffer-dmaengine.h               |   5 +
 2 files changed, 81 insertions(+), 31 deletions(-)

diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
index 054af21dfa65..602cb2e147a6 100644
--- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
+++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
@@ -33,6 +33,7 @@ struct dmaengine_buffer {
 	struct iio_dma_buffer_queue queue;
 
 	struct dma_chan *chan;
+	bool owns_chan;
 	struct list_head active;
 
 	size_t align;
@@ -216,28 +217,23 @@ 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.
  */
-static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
-	const char *channel)
+static struct iio_buffer *iio_dmaengine_buffer_alloc(struct dma_chan *chan,
+						     bool owns_chan)
 {
 	struct dmaengine_buffer *dmaengine_buffer;
 	unsigned int width, src_width, dest_width;
 	struct dma_slave_caps caps;
-	struct dma_chan *chan;
 	int ret;
 
 	dmaengine_buffer = kzalloc(sizeof(*dmaengine_buffer), GFP_KERNEL);
-	if (!dmaengine_buffer)
-		return ERR_PTR(-ENOMEM);
-
-	chan = dma_request_chan(dev, channel);
-	if (IS_ERR(chan)) {
-		ret = PTR_ERR(chan);
-		goto err_free;
+	if (!dmaengine_buffer) {
+		ret = -ENOMEM;
+		goto err_release;
 	}
 
 	ret = dma_get_slave_caps(chan, &caps);
 	if (ret < 0)
-		goto err_release;
+		goto err_free;
 
 	/* Needs to be aligned to the maximum of the minimums */
 	if (caps.src_addr_widths)
@@ -252,6 +248,7 @@ static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 
 	INIT_LIST_HEAD(&dmaengine_buffer->active);
 	dmaengine_buffer->chan = chan;
+	dmaengine_buffer->owns_chan = owns_chan;
 	dmaengine_buffer->align = width;
 	dmaengine_buffer->max_size = dma_get_max_seg_size(chan->device->dev);
 
@@ -263,10 +260,12 @@ static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 
 	return &dmaengine_buffer->queue.buffer;
 
-err_release:
-	dma_release_channel(chan);
 err_free:
 	kfree(dmaengine_buffer);
+err_release:
+	if (owns_chan)
+		dma_release_channel(chan);
+
 	return ERR_PTR(ret);
 }
 
@@ -282,12 +281,38 @@ void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
 		iio_buffer_to_dmaengine_buffer(buffer);
 
 	iio_dma_buffer_exit(&dmaengine_buffer->queue);
-	dma_release_channel(dmaengine_buffer->chan);
-
 	iio_buffer_put(buffer);
+
+	if (dmaengine_buffer->owns_chan)
+		dma_release_channel(dmaengine_buffer->chan);
 }
 EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_free, IIO_DMAENGINE_BUFFER);
 
+static struct iio_buffer
+*__iio_dmaengine_buffer_setup_ext(struct iio_dev *indio_dev,
+				  struct dma_chan *chan, bool owns_chan,
+				  enum iio_buffer_direction dir)
+{
+	struct iio_buffer *buffer;
+	int ret;
+
+	buffer = iio_dmaengine_buffer_alloc(chan, owns_chan);
+	if (IS_ERR(buffer))
+		return ERR_CAST(buffer);
+
+	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
+
+	buffer->direction = dir;
+
+	ret = iio_device_attach_buffer(indio_dev, buffer);
+	if (ret) {
+		iio_dmaengine_buffer_free(buffer);
+		return ERR_PTR(ret);
+	}
+
+	return buffer;
+}
+
 /**
  * iio_dmaengine_buffer_setup_ext() - Setup a DMA buffer for an IIO device
  * @dev: DMA channel consumer device
@@ -308,24 +333,13 @@ struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
 						  const char *channel,
 						  enum iio_buffer_direction dir)
 {
-	struct iio_buffer *buffer;
-	int ret;
-
-	buffer = iio_dmaengine_buffer_alloc(dev, channel);
-	if (IS_ERR(buffer))
-		return ERR_CAST(buffer);
-
-	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
-
-	buffer->direction = dir;
+	struct dma_chan *chan;
 
-	ret = iio_device_attach_buffer(indio_dev, buffer);
-	if (ret) {
-		iio_dmaengine_buffer_free(buffer);
-		return ERR_PTR(ret);
-	}
+	chan = dma_request_chan(dev, channel);
+	if (IS_ERR(chan))
+		return ERR_CAST(chan);
 
-	return buffer;
+	return __iio_dmaengine_buffer_setup_ext(indio_dev, chan, true, dir);
 }
 EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_setup_ext, IIO_DMAENGINE_BUFFER);
 
@@ -362,6 +376,37 @@ int devm_iio_dmaengine_buffer_setup_ext(struct device *dev,
 }
 EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_ext, IIO_DMAENGINE_BUFFER);
 
+/**
+ * devm_iio_dmaengine_buffer_setup_ext2() - Setup a DMA buffer for an IIO device
+ * @dev: Device for devm ownership
+ * @indio_dev: IIO device to which to attach this buffer.
+ * @chan: DMA channel
+ * @dir: Direction of buffer (in or out)
+ *
+ * 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.
+ *
+ * This is the same as devm_iio_dmaengine_buffer_setup_ext() except that the
+ * caller manages requesting and releasing the DMA channel.
+ */
+int devm_iio_dmaengine_buffer_setup_ext2(struct device *dev,
+					 struct iio_dev *indio_dev,
+					 struct dma_chan *chan,
+					 enum iio_buffer_direction dir)
+{
+	struct iio_buffer *buffer;
+
+	buffer = __iio_dmaengine_buffer_setup_ext(indio_dev, chan, false, dir);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	return devm_add_action_or_reset(dev, __devm_iio_dmaengine_buffer_free,
+					buffer);
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_ext2, IIO_DMAENGINE_BUFFER);
+
 MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
 MODULE_DESCRIPTION("DMA buffer for the IIO framework");
 MODULE_LICENSE("GPL");
diff --git a/include/linux/iio/buffer-dmaengine.h b/include/linux/iio/buffer-dmaengine.h
index 81d9a19aeb91..7bdb979b59f2 100644
--- a/include/linux/iio/buffer-dmaengine.h
+++ b/include/linux/iio/buffer-dmaengine.h
@@ -11,6 +11,7 @@
 
 struct iio_dev;
 struct device;
+struct dma_chan;
 
 void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
 struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
@@ -26,6 +27,10 @@ int devm_iio_dmaengine_buffer_setup_ext(struct device *dev,
 					struct iio_dev *indio_dev,
 					const char *channel,
 					enum iio_buffer_direction dir);
+int devm_iio_dmaengine_buffer_setup_ext2(struct device *dev,
+					 struct iio_dev *indio_dev,
+					 struct dma_chan *chan,
+					 enum iio_buffer_direction dir);
 
 #define devm_iio_dmaengine_buffer_setup(dev, indio_dev, channel)	\
 	devm_iio_dmaengine_buffer_setup_ext(dev, indio_dev, channel,	\

-- 
2.43.0