[PATCH v5 0/7] mfd: nct6694: Refactor transport layer and add HIF (eSPI) support

From: Ming Yu <redacted>

The Nuvoton NCT6694 is a peripheral expander that provides GPIO, I2C,
CAN-FD, Watchdog, HWMON, PWM, and RTC sub-devices. Currently, the
driver only supports USB as the host transport interface.

This series refactors the NCT6694 MFD core to support multiple transport
backends and adds a new Host Interface (HIF) transport driver that
communicates over eSPI using Super-I/O shared memory.

Changes since version 4:
- Split the monolithic refactoring and HIF support patch into a series of
  smaller, logical commits to improve reviewability and adhere to the
  single logical change principle.
- Decoupled USB-specific data into a dedicated 'nct6694_usb_data' 
  structure.
- Abstracted device I/O operations by introducing 'read_msg' and 
  'write_msg' function pointers in the core structure.
- Renamed the existing driver to 'nct6694-usb.c' to strictly identify its
  transport boundary, alongside Kconfig/Makefile updates.
- Extracted transport-agnostic device management (IRQ domain setup, IDA
  initialization, and MFD cell registration) into a standalone
  'nct6694-core.c' module.
- Added the 'nct6694-hif' eSPI transport driver clean on top of the new
  core abstraction.

Changes since version 3:
- Remove redundant module type macro definitions from sub-device drivers
  that are now provided by the shared header <linux/mfd/nct6694.h>,
  fixing -Wmacro-redefined warnings.

Changes since version 2:
- Restore per-device IDA and mfd_add_hotplug_devices()/PLATFORM_DEVID_AUTO
  to avoid child device ID conflicts with multiple NCT6694 chips.
- Validate irq_find_mapping() return value before dispatching IRQs.
- Check superio_enter() return value in nct6694_irq_init().

Changes since version 1:
- Reworked the Super-I/O access helpers.

Ming Yu (7):
  mfd: nct6694: Move module type macros to shared header
  mfd: nct6694: Refactor USB-specific data into nct6694_usb_data
  mfd: nct6694: Introduce transport abstraction with function pointers
  mfd: nct6694: Rename static I/O functions with _usb_ prefix
  mfd: nct6694: Rename driver to nct6694-usb and update Kconfig
  mfd: nct6694: Extract core device management into a separate module
  mfd: nct6694: Add Host Interface (HIF) eSPI transport driver

 MAINTAINERS                              |   2 +-
 drivers/gpio/gpio-nct6694.c              |   7 -
 drivers/hwmon/nct6694-hwmon.c            |  21 -
 drivers/i2c/busses/i2c-nct6694.c         |   7 -
 drivers/mfd/Kconfig                      |  38 +-
 drivers/mfd/Makefile                     |   4 +-
 drivers/mfd/nct6694-core.c               | 136 ++++++
 drivers/mfd/nct6694-hif.c                | 529 +++++++++++++++++++++++
 drivers/mfd/{nct6694.c => nct6694-usb.c} | 185 +++-----
 drivers/net/can/usb/nct6694_canfd.c      |   6 -
 drivers/rtc/rtc-nct6694.c                |   7 -
 drivers/watchdog/nct6694_wdt.c           |   7 -
 include/linux/mfd/nct6694.h              |  63 ++-
 13 files changed, 821 insertions(+), 191 deletions(-)
 create mode 100644 drivers/mfd/nct6694-core.c
 create mode 100644 drivers/mfd/nct6694-hif.c
 rename drivers/mfd/{nct6694.c => nct6694-usb.c} (62%)

-- 
2.34.1