Re: [PATCH v2 0/2] Sanity-check available_scan_masks array

[Matti Vaittinen]

On 10/21/23 18:55, Jonathan Cameron wrote:
> On Mon, 16 Oct 2023 14:04:11 +0300
> Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
>
> > 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(+)
>
> Hi Matti,
>
> Just a quick note to say this looks fine to me, but I don't want to queue it up
> just yet given proximity to merge window etc.

Makes perfect sense to me.

>  I'll aim to pick it up early
> in next cycle. Give me a poke if I still haven't by rc3 or so.

Ouch... My memory gets worse year by year - well, I'll try to remember :)

Yours,
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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