[PATCH v2 0/2] iio: light: isl29018: overflow fix + cover-glass gain via DT

[Herman van Hazendonk <github.com@herrie.org>]

v2: split into two patches after review feedback on v1.

PATCH 1/2 fixes a pre-existing 32-bit overflow in isl29018_read_lux()
that the reviewer correctly identified: lux_data * scale.uscale can
reach ~64 billion at full-scale 16-bit readings (65535 × 976562),
overflowing UINT_MAX before the /1000000 division.  A second overflow
occurs when the result is multiplied by calibscale and stored in the
signed int *lux.  Both are fixed by widening intermediate arithmetic to
u64 and clamping the output.

PATCH 2/2 is unchanged from v1: it adds the "isil,cover-comp-gain" DT
property to seed calibscale at probe time, following the precedent set
by tsl2563.c (amstaos,cover-comp-gain).  The default stays 1 so
existing systems are unaffected.  The overflow fix in patch 1 is a
natural prerequisite because patch 2 makes large calibscale values
straightforward to deploy from firmware.

A follow-up DTS patch enabling this for the HP TouchPad will be sent
separately to the ARM/DTS tree once the driver change is upstream.

Herman van Hazendonk (2):
  iio: light: isl29018: fix 32-bit overflow in isl29018_read_lux()
  iio: light: isl29018: support cover-glass gain compensation via DT

 .../bindings/iio/light/isl29018.yaml          | 13 ++++++++++++
 drivers/iio/light/isl29018.c                  | 20 ++++++++++++++-----
 2 files changed, 28 insertions(+), 5 deletions(-)


base-commit: 944125b4c454b58d2fe6e35f1087a932b2050dff
-- 
2.43.0