Rework cyclic block enqueue when talking to v0.x IIOD

Instead of continuously sending the same block again and again, set the
"cyclic" parameter of the .enable_buffer() backend callback to the value
of the "cyclic" parameter of the last call to iio_buffer_enqueue().

Signed-off-by: Paul Cercueil <paul@crapouillou.net>

block.c

@@ -19,9 +19,8 @@ struct iio_block {
 	size_t size;
 	void *data;
 
-	struct iio_task_token *token, *old_token;
+	struct iio_task_token *token;
 	size_t bytes_used;
-	bool cyclic;
 };
 
 struct iio_block *
@@ -83,9 +82,6 @@ void iio_block_destroy(struct iio_block *block)
 	struct iio_buffer *buf = block->buffer;
 	const struct iio_backend_ops *ops = buf->dev->ctx->ops;
 
-	/* Stop the cyclic task */
-	block->cyclic = false;
-
 	if (block->token) {
 		iio_task_cancel(block->token);
 		iio_task_sync(block->token, 0);
@@ -132,20 +128,12 @@ int iio_block_io(struct iio_block *block)
 	if (!iio_device_is_tx(block->buffer->dev))
 		return iio_block_read(block);
 
-	if (block->old_token)
-		iio_task_sync(block->old_token, 0);
-
-	if (block->cyclic) {
-		block->old_token = block->token;
-		block->token = iio_task_enqueue(block->buffer->worker, block);
-	}
-
 	return iio_block_write(block);
 }
 
 int iio_block_enqueue(struct iio_block *block, size_t bytes_used, bool cyclic)
 {
-	const struct iio_buffer *buffer = block->buffer;
+	struct iio_buffer *buffer = block->buffer;
 	const struct iio_device *dev = buffer->dev;
 	const struct iio_backend_ops *ops = dev->ctx->ops;
 
@@ -164,7 +152,7 @@ int iio_block_enqueue(struct iio_block *block, size_t bytes_used, bool cyclic)
 	}
 
 	block->bytes_used = bytes_used;
-	block->cyclic = cyclic;
+	buffer->cyclic = cyclic;
 	block->token = iio_task_enqueue(buffer->worker, block);
 
 	return iio_err(block->token);

buffer.c

@@ -51,6 +51,7 @@ static int iio_buffer_set_enabled(const struct iio_buffer *buf, bool enabled)
 	if (buf->block_size) {
 		sample_size = iio_device_get_sample_size(buf->dev, buf->mask);
 		nb_samples = buf->block_size / sample_size;
+		cyclic = buf->cyclic;
 	}
 
 	if (ops->enable_buffer)

iio-private.h

@@ -146,7 +146,10 @@ struct iio_buffer {
 
 	struct iio_task *worker;
 
+	/* These two fields are set by the last block created. They are only
+	 * used when communicating with v0.x IIOD. */
 	size_t block_size;
+	bool cyclic;
 
 	struct iio_attr_list attrlist;