[PATCH v9 00/11] iio: adc: Add support for AVIA HX710B ADC

[Piyush Patle <piyushpatle228@gmail.com>]

The HX710B is a 24-bit ADC from AVIA Semiconductor, related to the
HX711 already supported in this driver.  Unlike the HX711 (which has
selectable gain and two input channels), the HX710B has a fixed gain
of 128 and two operating modes selected by the trailing PD_SCK pulse
count after each conversion:

  25 pulses (1 trailing): differential input at 10 SPS
  26 pulses (2 trailing): DVDD-AVDD supply monitor at 40 SPS
  27 pulses (3 trailing): differential input at 40 SPS

This series first extends the existing HX711 binding and driver with
preparatory refactoring, then adds HX710B support on top.

The differential input is exposed as a single IIO channel with
IIO_CHAN_INFO_SAMP_FREQ, allowing userspace to select 10 or 40 SPS
without needing two separate channels for the same physical input.
The supply monitor is a second channel at fixed 40 SPS.

Patches 01/11, 02/11, 03/11, and 05/11 have already been applied to
the iio.git testing branch.  They are re-included here so the series
applies cleanly as a unit.

Changes from v8:
  - 04/11: Dropped a misleading sentence from the commit message that
    suggested HX711-only binding extensions live in earlier patches
    (they do not; the earlier patches extend the shared binding).
  - 06/11: No code change.  Added a note below the --- line clarifying
    that __counted_by_ptr() is available since 6.12 (this tree is
    6.17), so the annotation is well-defined.
  - 11/11: Redesigned HX710B channel layout per Jonathan's v8 review.
    Modes 1 and 3 both read the same physical differential input, so
    they are now a single IIO channel with IIO_CHAN_INFO_SAMP_FREQ
    instead of two separate channels.  Added hx710b_write_raw() and
    hx710b_read_avail() to let userspace control the sample rate.
    Introduced hx710b_trailing_pulses() helper so .address is no longer
    needed in the channel spec.  Fixed hx711_trigger() to check the
    return value of hx711_reset_read() and bail out on error.  Fixed
    channel_set update ordering in hx711_set_hx710b_channel() so the
    field is written immediately after hx711_read() commits the new
    hardware mode, before waiting for the chip to be ready.

Piyush Patle (11):
  dt-bindings: iio: adc: hx711: clean up existing binding text
  dt-bindings: iio: adc: hx711: add VSUP supply property
  dt-bindings: iio: adc: hx711: add RATE GPIO property
  dt-bindings: iio: adc: hx711: add HX710B support
  iio: adc: hx711: move scale computation to per-device storage
  iio: adc: hx711: introduce hx711_chip_info structure
  iio: adc: hx711: pass trailing pulse count into hx711_read
  iio: adc: hx711: split variable assignments in hx711_read and
    hx711_reset
  iio: adc: hx711: localize loop iterators in hx711_read
  iio: adc: hx711: pass iio_chan_spec to hx711_reset_read
  iio: adc: hx711: add support for HX710B

 .../bindings/iio/adc/avia-hx711.yaml          |  77 +++-
 drivers/iio/adc/Kconfig                       |   8 +-
 drivers/iio/adc/hx711.c                       | 362 ++++++++++++++----
 3 files changed, 362 insertions(+), 85 deletions(-)

-- 
2.43.0