Sanity-check available_scan_masks array The available_scan_masks is an array of bitmasks representing the channels which can be simultaneously(*) scanned by a driver from the device. Following special characteristics apply: - When IIO is scanning through the array it will use the first mask which can be used to scan all enabled channels. This means drivers should order the array in the order of the preference. This does also mean that a mask which is a subset of a mask located earler in array will never be used because the earlier one will be picked by the core. - Masks wider than size of long are supported only to some extent. The code scanning through the array will interpret the first mask with first long zeroed as end-of-array terminator. Changing this behaviour would make mask-arrays for multi-long masks to be terminated by more than one zero long. Failure to do so would result kernel to read beyond the array generating a potentially hazardous bug. Add a sanity-check to IIO-device registration emitting a warning if available_scan_mask array is misordered or if mask width is larger than a long while available_scan_mask-array is populated. Currently there should be no in-tree drivers with available_scan_mask populated and mask wider than a long. Revision history: v1 => v2: - Add patch 2/2 documenting why iio_scan_mask_match() checks only a long worth of bits while searching for the end of the available_scan_mask-array. - Styling of patch 1/2 as per comments from Jonathan v1 and related discussion here: https://lore.kernel.org/lkml/ZRvjuZaQWdZw1U1I@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ Matti Vaittinen (2): iio: sanity check available_scan_masks array iio: buffer: document known issue drivers/iio/industrialio-buffer.c | 16 ++++++++ drivers/iio/industrialio-core.c | 63 +++++++++++++++++++++++++++++++ 2 files changed, 79 insertions(+) -- 2.41.0 -- Matti Vaittinen, Linux device drivers ROHM Semiconductors, Finland SWDC Kiviharjunlenkki 1E 90220 OULU FINLAND ~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~ Simon says - in Latin please. ~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~ Thanks to Simon Glass for the translation =]
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