[PATCH v4 0/6] iio: dac: ad5504: bindings, cleanups, locking, and scale fixes

This v4 series continues the cleanup and scale-fix work for the AD5504
high-voltage DAC driver, addressing all outstanding feedback from the v3 review.

Jonathan Cameron applied patches 2 (sort headers alphabetically) and 4
(introduce local dev pointer) from v3 directly to iio/testing. This series
rebases on top of that state and does not re-send those patches.

Changes in v4:

* Split the formerly monolithic v3 patch 5 into four focused commits:
  pdata removal, locking, ACPI/DT separation, and output-range support.
  Each commit leaves the driver in a clean, bisectable state.
* Fix ACPI probe path by forking on ACPI_COMPANION() instead of relying
  on the -ENODEV sentinel from the regulator framework, following the
  pattern established in adc/ti-ads7950.c (David Lechner).
* Introduce a mutex via devm_mutex_init() and guard(mutex) to fix three
  concurrency issues: shared DMA SPI buffers, non-atomic CTRL+NOOP write
  sequences, and unprotected pwr_down_mask/pwr_down_mode state.
* Use device_property_present() to cleanly distinguish "property absent"
  from "property present but malformed" when parsing
  output-range-microvolt, replacing the ambiguous -EINVAL sentinel.
* Add backward compatibility fallback via
  devm_regulator_get_enable_read_voltage() for old DTs that predate the
  output-range-microvolt property.
* Replace <linux/device.h> with <linux/dev_printk.h> in IWYU patch
  (Jonathan Cameron).

Testing:
Verified on ARM64 Raspberry Pi 5 (BCM2712) using a custom Device Tree
overlay on spi10, without physical AD5504 hardware.

60V path (output-range-microvolt = <0 60000000>):
$ cat /sys/bus/iio/devices/iio:device0/out_voltage_scale
14.648437500  (60000 mV / 4096)

30V path (output-range-microvolt = <0 30000000>):
$ cat /sys/bus/iio/devices/iio:device0/out_voltage_scale
7.324218750   (30000 mV / 4096)

Invalid range (output-range-microvolt = <0 70000000>):
[   40.646862] ad5504 spi10.0: error -EINVAL: Invalid output-range-microvolt
[   40.646869] ad5504 spi10.0: probe with driver ad5504 failed with error -22

Backward compatibility (no output-range-microvolt, vcc-supply = 60V):
$ cat /sys/bus/iio/devices/iio:device0/out_voltage_scale
14.648437500  (60000 mV / 4096 via regulator fallback)

Powerdown sysfs read/write and powerdown mode switching (20kohm_to_gnd,
three_state) verified on all four channels without errors.

Previous versions:
v3: https://lore.kernel.org/linux-iio/[email protected]/
v2: https://lore.kernel.org/linux-iio/[email protected]/
v1: https://lore.kernel.org/linux-iio/[email protected]/

Thank you to Jonathan Cameron, David Lechner, Andy Shevchenko, Nuno Sá,
Krzysztof Kozlowski, and Conor Dooley for the continued reviews.

Taha Ed-Dafili (6):
  dt-bindings: iio: dac: ad5504: add output-range and missing gpios
  iio: dac: ad5504: Align headers with IWYU principle
  iio: dac: ad5504: remove legacy platform data support
  iio: dac: ad5504: introduce local lock to protect state and spi
    transfers
  iio: dac: ad5504: strictly separate ACPI and DT probe paths
  iio: dac: ad5504: support scale via output-range-microvolt property

 .../bindings/iio/dac/adi,ad5504.yaml          | 39 +++++++++-
 drivers/iio/dac/ad5504.c                      | 76 ++++++++++++++-----
 include/linux/iio/dac/ad5504.h                | 15 ----
 3 files changed, 97 insertions(+), 33 deletions(-)
 delete mode 100644 include/linux/iio/dac/ad5504.h

-- 
2.55.0