[PATCH v3 0/3] iio: adc: add LTC2499 features support

[Andrei Stancovici <andrei.stancovici@analog.com>]

This series adds LTC2499 support on top of the existing LTC2497 driver.

It includes:
- a small binding title correction for LTC2499,
- the LTC2499 internal temperature channel,
- the LTC2499 2x conversion speed mode exposed via sampling_frequency.

Validation performed on Raspberry Pi 4 with a DC1012A-A board:
- temperature raw/scale/offset read correctly,
- voltage channels remain sane after temperature reads,
- sampling_frequency 1x/2x switching works,
- pyadi-iio LTC2499 validation passed,
- hardware-in-the-loop M2K validation passed.

Changes in v2:
- guard against regulator_get_voltage() returning 0 in the temperature offset path,
- replace LTC2499 two-byte stack command buffers with a DMA-safe buffer,
- use ABSOLUTE_ZERO_MILLICELSIUS and standard SI unit multipliers,
- make channel-count handling explicit,
- clean up includes and iterator usage,
- update conversion-state handling for interrupted waits,
- clarify conversion-time rounding and LTC2499 configuration behavior.

Changes in v3:
- revert the LTC2499 two-byte command path to a local stack buffer and remove the incorrect DMA-safe rationale
- use a standard zero-value comparison in the temperature offset path
- simplify the temperature offset derivation comments
- simplify the temperature offset computation
- adjust ltc2497_chip_info field placement based on pahole analysis
- apply review-driven comment and formatting cleanups

Andrei Stancovici (3):
  dt-bindings: iio: adc: lltc,ltc2497: add LTC2499 to title
  iio: adc: ltc2497: add LTC2499 internal temperature channel
  iio: adc: ltc2497: add 2x conversion speed mode

 .../bindings/iio/adc/lltc,ltc2497.yaml        |   2 +-
 drivers/iio/adc/ltc2497-core.c                | 235 +++++++++++++++++-
 drivers/iio/adc/ltc2497.c                     |  39 +++
 drivers/iio/adc/ltc2497.h                     |  46 +++-
 4 files changed, 309 insertions(+), 13 deletions(-)

-- 
2.43.0