[PATCH v8 00/13] mfd: nct6694: Refactor transport layer and add HIF (eSPI) support

[a0282524688@gmail.com]

From: Ming Yu <a0282524688@gmail.com>

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 driver to support multiple
transport backends and adds a Host Interface (HIF) transport driver
that communicates over eSPI using Super-I/O shared memory.

Patches 1-5 fix pre-existing bugs in the current driver. They carry a
Fixes tag and can be picked up independently of the rest of the series.

Patches 6-12 isolate the USB transport, extract the transport-agnostic
core into nct6694-core.c and wrap the firmware command interface behind
regmap, so that the sub-device drivers no longer depend on the
transport. Patch 13 adds the HIF transport on top.

Changes since version 7:
- Marked the GPIO controller as sleeping.
- Validated the USB endpoints with usb_check_{bulk,int}_endpoints().
- Checked the length of received USB packets.
- Ignored interrupts without a mapping.
- Moved all fixes to the start of the series.
- Embedded struct nct6694 in the transport data and dropped the priv
  pointer.
- Renamed variables and buffers consistently.
- Retrieved struct nct6694 from the driver data in the core, and let the
  transports register their own MFD cells.
- Returned -ENOMEM when the IRQ domain cannot be created.
- Kept MFD_NCT6694 as the core symbol and added MFD_NCT6694_USB.
- Folded the interrupt URB submission fix into the core extraction.
- HIF: requested the interrupt after the core is set up, so that it is
  freed before the IRQ domain is removed.

Changes since version 6:
- Transfer command payloads through a buffer owned by the transport.
- Locate the interrupt IN endpoint with usb_find_int_in_endpoint().
- Submit the interrupt URB after the core has created the IRQ domain.
- HIF: several robustness fixes in the interrupt and shared memory
  setup.

Changes since version 5:
- Replaced the read_msg/write_msg function pointers with a regmap-based
  transport abstraction, and added nct6694_write_read_msg().

Changes since version 4:
- Split the monolithic patch into a series of logical commits.

Changes since version 3:
- Removed redundant module type macro definitions from the sub-device
  drivers.

Changes since version 2:
- Restored per-device IDA and PLATFORM_DEVID_AUTO.
- Validated the irq_find_mapping() return value.
- Checked the superio_enter() return value.

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

Ming Yu (13):
  gpio: nct6694: Mark the GPIO controller as sleeping
  mfd: nct6694: Validate the USB endpoints
  mfd: nct6694: Check the length of received USB packets
  mfd: nct6694: Ignore interrupts without a mapping
  mfd: nct6694: Transfer data packets via a dedicated buffer
  mfd: nct6694: Move module type macros to shared header
  mfd: nct6694: Refactor USB-specific data into nct6694_usb_data
  mfd: nct6694: Rename USB transport functions with _usb_ prefix
  mfd: nct6694: Rename driver to nct6694-usb
  mfd: nct6694: Extract core device management into a separate module
  mfd: nct6694: Introduce regmap-based transport abstraction
  mfd: nct6694: Add a Kconfig symbol for the USB transport
  mfd: nct6694: Add Host Interface (HIF) eSPI transport driver

 MAINTAINERS                         |   2 +-
 drivers/gpio/gpio-nct6694.c         |   9 +-
 drivers/hwmon/nct6694-hwmon.c       |  21 -
 drivers/i2c/busses/i2c-nct6694.c    |   9 +-
 drivers/mfd/Kconfig                 |  34 +-
 drivers/mfd/Makefile                |   4 +-
 drivers/mfd/nct6694-core.c          | 111 ++++++
 drivers/mfd/nct6694-hif.c           | 572 ++++++++++++++++++++++++++++
 drivers/mfd/nct6694-usb.c           | 414 ++++++++++++++++++++
 drivers/mfd/nct6694.c               | 388 -------------------
 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         |  91 ++++-
 14 files changed, 1205 insertions(+), 470 deletions(-)
 create mode 100644 drivers/mfd/nct6694-core.c
 create mode 100644 drivers/mfd/nct6694-hif.c
 create mode 100644 drivers/mfd/nct6694-usb.c
 delete mode 100644 drivers/mfd/nct6694.c

-- 
2.34.1