[PATCH v6 0/3] gpio: Add AD7768 GPIO support

[Janani Sunil <janani.sunil@analog.com>]

Add GPIO support for the Analog Devices AD7768 and AD7768-4
simultaneous sampling ADCs.

Datasheet:
https://www.analog.com/media/en/technical-documentation/data-sheets/ad7768-ad7768-4.pdf

**Device Overview:**
The AD7768 and AD7768-4 provide five on-chip GPIO pins controlled
through registers shared with the parent IIO device. The GPIO driver is
registered as an auxiliary driver and shares the parent's regmap and
runtime power-management state.

**Features Implemented:**
- Use regmap_test_bits() for single-bit gpio-regmap value and direction
  reads.
- Add optional runtime PM support to gpio-regmap.
- Expose the five AD7768 GPIO pins through gpio-regmap.
- Read output GPIO values from the output-latch register while retaining
  input-state reads for input pins.
- Reserve GPIO4 when it is used to select the crystal or LVDS master
  clock source.

**Patch Summary:**
1. Use regmap_test_bits() for single-bit gpio-regmap reads.
2. Add optional runtime PM support to gpio-regmap.
3. Add the AD7768 GPIO auxiliary driver.

**Testing:**
The complete AD7768 driver was compiled and tested on the
EVAL-AD7768FMCZ using a Zedboard with a mainline kernel.

**Base:**
This series is based on the GPIO subsystem's gpio/for-next branch,
commit a2cfc48fee416f0ea78e7dc38acbf2ce072574cc

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
Changes in v6:
- Split the GPIO patches from the main AD7768 IIO series.
- Rebase onto gpio/for-next commit
  a2cfc48fee416f0ea78e7dc38acbf2ce072574cc.
- Adapt the gpio-regmap callbacks to the operation argument present in
  gpio/for-next.
- Align the gpio-regmap runtime-PM member layout with review feedback.
- Move GPIO valid-mask handling into the GPIO driver and reserve GPIO4
  there when it is used for crystal or LVDS clock selection.
- Link to v5: https://lore.kernel.org/r/20260828-ad7768-driver-v5-0-e33ca6f841a2@analog.com

---
Janani Sunil (3):
      gpio: regmap: Use regmap_test_bits() for single bit reads
      gpio: regmap: Add optional runtime PM support
      gpio: ad7768: Add AD7768 GPIO auxiliary driver

 drivers/gpio/Kconfig        |  12 +++++
 drivers/gpio/Makefile       |   1 +
 drivers/gpio/gpio-ad7768.c  | 122 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpio-regmap.c  |  98 +++++++++++++++++++++++++++++------
 include/linux/gpio/regmap.h |   2 +
 5 files changed, 220 insertions(+), 15 deletions(-)
---
base-commit: a2cfc48fee416f0ea78e7dc38acbf2ce072574cc
change-id: 20260903-ad7768-gpio-4a19153b1470

Best regards,
-- 
Janani Sunil <janani.sunil@analog.com>