[PATCH v2 0/7] regulator: new API for voltage reference supplies

[David Lechner]

In the IIO subsystem, we noticed a pattern in many drivers where we need
to get, enable and get the voltage of a supply that provides a reference
voltage. In these cases, we only need the voltage and not a handle to
the regulator. Another common pattern is for chips to have an internal
reference voltage that is used when an external reference is not
available. There are also a few drivers outside of IIO that do the same.

So we would like to propose a new regulator consumer API to handle these
specific cases to avoid repeating the same boilerplate code in multiple
drivers.

As an example of how these functions are used, I have included a few
patches to consumer drivers. But to avoid a giant patch bomb, I have
omitted the iio/adc and iio/dac patches I have prepared from this
series. I will send those separately but these will add 36 more users
of devm_regulator_get_enable_read_voltage() in addition to the 6 here.
In total, this will eliminate nearly 1000 lines of similar code and will
simplify writing and reviewing new drivers in the future.

---
Changes in v2:
- Reworked regulator patch to remove dev_err_probe() and properly unwind
- Combined two proposed functions into a single function
- Renamed function to devm_regulator_get_enable_read_voltage() everywhere
- Fixed other feedback on consumer patches (see individual patches)
- Picked up Jonathan's Reviewed-bys (hopefully changes were trivial enough)
- Link to v1: https://lore.kernel.org/r/20240327-regulator-get-enable-get-votlage-v1-0-5f4517faa059@xxxxxxxxxxxx

---
David Lechner (7):
      regulator: devres: add API for reference voltage supplies
      hwmon: (adc128d818) Use devm_regulator_get_enable_read_voltage()
      hwmon: (da9052) Use devm_regulator_get_enable_read_voltage()
      iio: addac: ad74115: Use devm_regulator_get_enable_read_voltage()
      iio: frequency: admv1013: Use devm_regulator_get_enable_read_voltage()
      staging: iio: impedance-analyzer: ad5933: Use devm_regulator_get_enable_read_voltage()
      Input: mpr121: Use devm_regulator_get_enable_read_voltage()

 Documentation/driver-api/driver-model/devres.rst |  1 +
 drivers/hwmon/adc128d818.c                       | 57 +++++++----------------
 drivers/hwmon/da9052-hwmon.c                     | 38 ++++-----------
 drivers/iio/addac/ad74115.c                      | 40 ++++++----------
 drivers/iio/frequency/admv1013.c                 | 40 ++++------------
 drivers/input/keyboard/mpr121_touchkey.c         | 45 ++----------------
 drivers/regulator/devres.c                       | 59 ++++++++++++++++++++++++
 drivers/staging/iio/impedance-analyzer/ad5933.c  | 26 +----------
 include/linux/regulator/consumer.h               |  7 +++
 9 files changed, 124 insertions(+), 189 deletions(-)
---
base-commit: 84c1815e46bdcb8bb0259db3d6cdd934cb70a0e9
change-id: 20240326-regulator-get-enable-get-votlage-5dedf40ff338