[PATCH v4 0/4] iio: light: tsl2591: fix lux calculation and precision, add I2C ID table, report saturation

[Jan Remes <ciakval@gmail.com>]

This series fixes several issues found while using the TSL2591 in
company products (Raspberry Pi CM5) and when testing (x86_64 laptops
with MCP2221 USB-I2C bridge).

The original field report found that the illumination value has always
been 0.0 (caused by division by zero on ARM).

Patch 1 fixes divisions by zero in the lux calculation, which occur with
LOW gain and short integration times, or in darkness when CH0 = 0.

Patch 2 adds an i2c_device_id table so the driver can be matched by name
(e.g. via sysfs new_device) on kernels without CONFIG_OF.

Patch 3 makes the driver return an error instead of a bogus value when the
sensor is saturated.

Patch 4 improves the formula for calculating lux values to make the
returned value more accurate.

Patches 3 and 4 change existing behavior, I am OK with splitting the
series into two, if that makes things better.

AI assistance: Claude Code (Claude Opus 5.5) was used for research on
sensor behavior, datasheets and Adafruit library, to compare results
produced by old and new formula, to draft some code for patches 1 and 4.
I reviewed all of it and tested it on x86_64.

---
Changes in v4:
- no changes in the code
- drop "Assisted-by: LLM" tags (Andy)
- Patch 2: make commit message more to the point (Andy)
- Link to v3: https://patch.msgid.link/20261022-first-patch-v3-0-b792e89a429a@mycroftmind.com

Changes in v3:
- Patch 2: Fix commit message, OF-only drivers can still be enumerated via
  DT or ACPI (PRP0001), only matching by name needs the I2C ID table (Andy)
- Patch 2: Drop Andy's Reviewed-by
- Rebase on current iio/testing
- Link to v2: https://patch.msgid.link/20261014141650.259929-1-ciakval@gmail.com

Changes in v2 (thanks to Andy Shevchenko for review):
- Patch 2: Use C99 initializers
- Patch 4: Keep variables in reversed xmas tree order
- Link to v1: https://lore.kernel.org/r/20261013143943.436816-1-ciakval@gmail.com/

To: Jonathan Cameron <jic23@kernel.org>
To: David Lechner <dlechner@baylibre.com>
To: Nuno Sá <nuno.sa@analog.com>
To: Andy Shevchenko <andy@kernel.org>
To: Joe Sandom <joe.g.sandom@gmail.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: linux-iio@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Jan Remes <jan.remes@mycroftmind.com>

---
Jan Remes (4):
      iio: light: tsl2591: don't divide by zero
      iio: light: tsl2591: add I2C device ID table
      iio: light: tsl2591: report saturation
      iio: light: tsl2591: improve lux calculation precision

 drivers/iio/light/tsl2591.c | 58 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 16 deletions(-)
---
base-commit: 87e28db23d0384f3995c43ecc5ae2118b371edb5
change-id: 20261014-first-patch-23099c6002da

Best regards,
--  
Jan Remes <jan.remes@mycroftmind.com>