linux-kernel - [PATCH v3 0/4] Add LTC2495 support

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Message-Id: <20250814-ltc2495-v3-0-c2a6cecd6b99@gmail.com>
Date: Thu, 14 Aug 2025 13:00:16 +0200
From: Yusuf Alper Bilgin <y.alperbilgin@...il.com>
To: Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Liam Beguin <liambeguin@...il.com>
Cc: Michael Hennerich <michael.hennerich@...log.com>, 
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Yusuf Alper Bilgin <y.alperbilgin@...il.com>
Subject: [PATCH v3 0/4] Add LTC2495 support

Hi All,

This is the v3 of the patch series adding support for the LTC2495 ADC in
the ltc2497 driver, and enabling the internal temperature channel for
the LTC2495 and LTC2499.

Thanks to Andy Shevchenko for his quick, helpful, and continued review
of the previous version.

In response to the request to check for code size changes, I have run
`bloat-o-meter`. The results confirm no meaningful impact on code size.

Full bloat-o-meter output:
```
./scripts/bloat-o-meter \
    before_patch_4/ltc2497-core.o drivers/iio/adc/ltc2497-core.o
add/remove: 0/0 grow/shrink: 1/1 up/down: 1/-1 (0)
Function                      old     new   delta
ltc2497core_read_raw          413     414      +1
ltc2497core_probe             374     373      -1
Total: Before=11576, After=11576, chg +0.00%

./scripts/bloat-o-meter \
    before_patch_4/ltc2497.o drivers/iio/adc/ltc2497.o
add/remove: 0/0 grow/shrink: 2/0 up/down: 2/0 (2)
Function                      old     new   delta
ltc2497_result_and_measure    275     276      +1
ltc2497_probe                 158     159      +1
Total: Before=1946, After=1948, chg +0.10%

./scripts/bloat-o-meter \
    before_patch_4/ltc2496.o drivers/iio/adc/ltc2496.o
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
Function                      old     new   delta
Total: Before=1251, After=1251, chg +0.00%
```

Best Regards,

Alper

Signed-off-by: Yusuf Alper Bilgin <y.alperbilgin@...il.com>
---
Changes in v3:
  - Used the standard `kelvin_to_celsius()` helper instead of a custom
    define.
  - Corrected macro definition style.
  - Renamed `LTC2497_CHANNELS` and `LTC_T_CHAN` for clarity.
  - Combined all struct layout optimizations into a single patch.
  - Link to v2: https://lore.kernel.org/r/20250813-ltc2495-v2-0-bbaf20f6ba07@gmail.com

Changes in v2:
  - Rewrote all commit messages to use the imperative mood.
  - Added a justification for the new compatible string to the device
    tree binding commit message.
  - Removed all unrelated whitespace and formatting changes.
  - Removed redundant explicit `false` initializers from structs.
  - Replaced the magic number for Kelvin conversion with a define.
  - Improved comments for defines and temperature scaling constants.
  - Renamed confusing macros and struct fields to be more descriptive.
  - Replaced dynamic channel allocation with a static array approach
    using a shared macro to improve readability.
  - Optimized data structure layouts based on pahole output to remove
    memory holes.
  - Link to v1: https://lore.kernel.org/r/20250812-ltc2495-v1-0-7bf4c6feec2e@gmail.com
---
Implementation Notes
 - checkpatch warning: The new static array approach uses a shared macro
   for the common channels (`LTC2497_CHANNELS`), which triggers a
   checkpatch.pl warning: "Macros with complex values should be enclosed
   in parentheses". However, this will cause a compilitaion error, as an
   initializer list cannot be parenthesized.
 - uV to mV conversion: I could not find a standard macro, so a manual
   division is used for now. This could be a point of future
   improvement.

---
Yusuf Alper Bilgin (4):
      dt-bindings: iio: adc: ltc2497: add lltc,ltc2495 bindings
      iio: adc: ltc2497: add support for LTC2495
      iio: adc: ltc2497: add temperature sensor support
      iio: adc: ltc2497: reorder struct members to fix memory holes

 .../devicetree/bindings/iio/adc/lltc,ltc2497.yaml  |   3 +
 drivers/iio/adc/ltc2497-core.c                     | 141 +++++++++++++++------
 drivers/iio/adc/ltc2497.c                          |  35 ++++-
 drivers/iio/adc/ltc2497.h                          |  23 +++-
 4 files changed, 159 insertions(+), 43 deletions(-)
---
base-commit: acbbb5a20971089064ca6b271dd251e629be8d4d
change-id: 20250811-ltc2495-572817c13fd3

Best regards,
-- 
Yusuf Alper Bilgin <y.alperbilgin@...il.com>