patch "iio: buffer: Fix demux update" added to staging-testing

This is a note to let you know that I've just added the patch titled

iio: buffer: Fix demux update

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the staging-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From 19ef7b70ca9487773c29b449adf0c70f540a0aab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nuno=20S=C3=A1?= <[email protected]>
Date: Thu, 12 Nov 2020 15:43:22 +0100
Subject: iio: buffer: Fix demux update
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When updating the buffer demux, we will skip a scan element from the device in the case in_ind != out_ind and we enter the while loop. in_ind should only be refreshed with find_next_bit() in the end of the loop.

Note, to cause problems we need a situation where we are skippig over an element (channel not enabled) that happens to not have the same size
as the next element. Whilst this is a possible situation we haven't
actually identified any cases in mainline where it happens as most drivers have consistent channel storage sizes with the exception of the timestamp which is the last element and hence never skipped over.

---
 drivers/iio/industrialio-buffer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 9663dec3dcf3..2f7426a2f47c 100644
@@ -853,12 +853,12 @@ static int iio_buffer_update_demux(struct iio_dev *indio_dev,
 				       indio_dev->masklength,
 				       in_ind + 1);
 		while (in_ind != out_ind) {
-			in_ind = find_next_bit(indio_dev->active_scan_mask,
-					       indio_dev->masklength,
-					       in_ind + 1);
 			length = iio_storage_bytes_for_si(indio_dev, in_ind);
 			/* Make sure we are aligned */
 			in_loc = roundup(in_loc, length) + length;
+			in_ind = find_next_bit(indio_dev->active_scan_mask,
+					       indio_dev->masklength,
+					       in_ind + 1);
 		}
 		length = iio_storage_bytes_for_si(indio_dev, in_ind);
 		out_loc = roundup(out_loc, length);

2.29.2