patch "iio: pressure: mpl115: do not rely on structure field ordering" added to staging-next

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

iio: pressure: mpl115: do not rely on structure field ordering

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-next 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 also be merged in the next major kernel release during the merge window.

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

From: Peter Rosin <[email protected]>
Date: Wed, 1 Feb 2017 21:40:57 +0100
Subject: iio: pressure: mpl115: do not rely on structure field ordering

Fixes a regression triggered by a change in the layout of struct iio_chan_spec, but the real bug is in the driver which assumed a specific structure layout in the first place. Hint: the three bits were not OR:ed together as implied by the indentation prior to this patch, there was a comma between the first two, which accidentally moved the ..._SCALE and ..._OFFSET bits to the next structure field. That field was .info_mask_shared_by_type before the _available attributes was added by commit 51239600074b ("iio:core: add a callback to allow drivers to provide _available attributes") and .info_mask_separate_available afterwards, and the regression happened.

info_mask_shared_by_type is actually a better choice than the originally intended info_mask_separate for the ..._SCALE and ..._OFFSET bits since a constant is returned from mpl115_read_raw for the scale/offset. Using info_mask_shared_by_type also preserves the behavior from before the regression and is therefore less likely to cause other interesting side effects.

The above mentioned regression causes unintended sysfs attibutes to show up that are not backed by code, in turn causing a NULL pointer defererence to happen on access.

---
 drivers/iio/pressure/mpl115.c | 1 +
 1 file changed, 1 insertion(+)

index 73f2f0c46e62..8f2bce213248 100644
@@ -137,6 +137,7 @@ static const struct iio_chan_spec mpl115_channels[] = {
 	{
 		.type = IIO_TEMP,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type =
 			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE),
 	},
 };

2.11.1