iio: __iio_update_buffers: Perform request_update() only for new buffers

We only have to call the request_update() callback for a newly inserted
buffer. The configuration of the already previously active buffers will not
have changed.

This also allows us to move the request_update() call to the beginning of
__iio_update_buffers(), before any currently active buffers are stopped.
This makes the error handling a lot easier since no changes were made to
the buffer list and no rollback needs to be performed.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 2afe3db..21ed316 100644 (file)
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -575,6 +575,25 @@ static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
        buffer->access->set_bytes_per_datum(buffer, bytes);
 }
 
+static int iio_buffer_request_update(struct iio_dev *indio_dev,
+       struct iio_buffer *buffer)
+{
+       int ret;
+
+       iio_buffer_update_bytes_per_datum(indio_dev, buffer);
+       if (buffer->access->request_update) {
+               ret = buffer->access->request_update(buffer);
+               if (ret) {
+                       dev_dbg(&indio_dev->dev,
+                              "Buffer not started: buffer parameter update failed (%d)\n",
+                               ret);
+                       return ret;
+               }
+       }
+
+       return 0;
+}
+
 static void iio_free_scan_mask(struct iio_dev *indio_dev,
        const unsigned long *mask)
 {
@@ -593,6 +612,12 @@ static int __iio_update_buffers(struct iio_dev *indio_dev,
        unsigned long *compound_mask;
        const unsigned long *old_mask;
 
+       if (insert_buffer) {
+               ret = iio_buffer_request_update(indio_dev, insert_buffer);
+               if (ret)
+                       return ret;
+       }
+
        /* Wind down existing buffers - iff there are any */
        if (!list_empty(&indio_dev->buffer_list)) {
                if (indio_dev->setup_ops->predisable) {
@@ -678,17 +703,6 @@ static int __iio_update_buffers(struct iio_dev *indio_dev,
                iio_compute_scan_bytes(indio_dev,
                                       indio_dev->active_scan_mask,
                                       indio_dev->scan_timestamp);
-       list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
-               iio_buffer_update_bytes_per_datum(indio_dev, buffer);
-               if (buffer->access->request_update) {
-                       ret = buffer->access->request_update(buffer);
-                       if (ret) {
-                               dev_dbg(&indio_dev->dev,
-                                      "Buffer not started: buffer parameter update failed (%d)\n", ret);
-                               goto error_run_postdisable;
-                       }
-               }
-       }
        if (indio_dev->info->update_scan_mode) {
                ret = indio_dev->info
                        ->update_scan_mode(indio_dev,