iio: buffer: introduce support for attaching more IIO buffers

With this change, calling iio_device_attach_buffer() will actually attach
more buffers.
Right now this doesn't do any validation of whether a buffer is attached
twice; maybe that can be added later (if needed). Attaching a buffer more
than once should yield noticeably bad results.

The first buffer is the legacy buffer, so a reference is kept to it.

At this point, accessing the data for the extra buffers (that are added
after the first one) isn't possible yet.

The iio_device_attach_buffer() is also changed to return an error code,
which for now is -ENOMEM if the array could not be realloc-ed for more
buffers.
To adapt to this new change iio_device_attach_buffer() is called last in
all place where it's called. The realloc failure is a bit difficult to
handle during un-managed calls when unwinding, so it's better to have this
as the last error in the setup_buffer calls.

At this point, no driver should call iio_device_attach_buffer() directly,
it should call one of the {devm_}iio_triggered_buffer_setup() or
devm_iio_kfifo_buffer_setup() or devm_iio_dmaengine_buffer_setup()
functions. This makes iio_device_attach_buffer() a bit easier to handle.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-20-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

3 files changed, 9 insertions, 9 deletions

diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
index a64b222289be..d76179878ff9 100644
--- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
+++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
@@ -290,9 +290,7 @@ int devm_iio_dmaengine_buffer_setup(struct device *dev,
 
 	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
 
-	iio_device_attach_buffer(indio_dev, buffer);
-
-	return 0;
+	return iio_device_attach_buffer(indio_dev, buffer);
 }
 EXPORT_SYMBOL_GPL(devm_iio_dmaengine_buffer_setup);
 
diff --git a/drivers/iio/buffer/industrialio-triggered-buffer.c b/drivers/iio/buffer/industrialio-triggered-buffer.c
index 92b8aea3e063..b2b1b7d27af4 100644
--- a/drivers/iio/buffer/industrialio-triggered-buffer.c
+++ b/drivers/iio/buffer/industrialio-triggered-buffer.c
@@ -50,8 +50,6 @@ int iio_triggered_buffer_setup_ext(struct iio_dev *indio_dev,
 		goto error_ret;
 	}
 
-	iio_device_attach_buffer(indio_dev, buffer);
-
 	indio_dev->pollfunc = iio_alloc_pollfunc(h,
 						 thread,
 						 IRQF_ONESHOT,
@@ -72,10 +70,16 @@ int iio_triggered_buffer_setup_ext(struct iio_dev *indio_dev,
 
 	buffer->attrs = buffer_attrs;
 
+	ret = iio_device_attach_buffer(indio_dev, buffer);
+	if (ret < 0)
+		goto error_dealloc_pollfunc;
+
 	return 0;
 
+error_dealloc_pollfunc:
+	iio_dealloc_pollfunc(indio_dev->pollfunc);
 error_kfifo_free:
-	iio_kfifo_free(indio_dev->buffer);
+	iio_kfifo_free(buffer);
 error_ret:
 	return ret;
 }
diff --git a/drivers/iio/buffer/kfifo_buf.c b/drivers/iio/buffer/kfifo_buf.c
index c35a625280b1..34289ce12f20 100644
--- a/drivers/iio/buffer/kfifo_buf.c
+++ b/drivers/iio/buffer/kfifo_buf.c
@@ -235,12 +235,10 @@ int devm_iio_kfifo_buffer_setup(struct device *dev,
 	if (!buffer)
 		return -ENOMEM;
 
-	iio_device_attach_buffer(indio_dev, buffer);
-
 	indio_dev->modes |= mode_flags;
 	indio_dev->setup_ops = setup_ops;
 
-	return 0;
+	return iio_device_attach_buffer(indio_dev, buffer);
 }
 EXPORT_SYMBOL_GPL(devm_iio_kfifo_buffer_setup);