[PATCH v4 0/5] serial: sc16is7xx: split into core and I2C/SPI parts

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>

Hello,
this patch series splits the SPI/I2C parts for the sc16is7xx driver into
separate source files (and separate I2C/SPI drivers).

These changes are based on suggestions made by Andy Shevchenko
following this discussion:

Link: https://lore.kernel.org/all/CAHp75VebCZckUrNraYQj9k=Mrn2kbYs1Lx26f5-8rKJ3RXeh-w@xxxxxxxxxxxxxx/

The changes are split into multiple patches to facilitate the review process.
In the end, some of them could be merged into a single patch.

I have tested the changes on a custom board with two SC16IS752 DUART over
a SPI interface using a Variscite IMX8MN NANO SOM. The four UARTs are
configured in RS-485 mode.

I did not test the changes on a real SC16is7xx using the I2C interface. But
I slightly modified the driver to be able to simulate an I2C device using
i2c-stub. I was then able to instantiate a virtual I2C device without
disturbing existing connection/communication between real SPI devices on
/dev/ttySC0 and /dev/ttySC2 (using a loopback cable).

Thank you.

Link: [v1] https://lore.kernel.org/lkml/20240206214208.2141067-1-hugo@xxxxxxxxxxx
      [v2] https://lore.kernel.org/lkml/20240307161828.118495-1-hugo@xxxxxxxxxxx
      [v3] https://lore.kernel.org/lkml/20240402174353.256627-1-hugo@xxxxxxxxxxx

Changes for V2:
- Move port_registered[] init before the for loop to prevent bug if
  aborting probe when i = 0
- Since patch f7b487648986 ("lib/find: add atomic find_bit() primitives") has
  been dropped from linux-next/master, rework patch 2 (sc16is7xx_lines)
  without find_and_set_bit.

Changes for V3:
- Simplify sc16is7xx_lines allocation by using the IDA framework

Changes for V4:
Changes after Andy S. review comments:
- Fix commit description
- Fix includes for IWYU
- Add Reviewed-by tag (Andy) for patches 1 and 5
- Add exported symbols to SERIAL_NXP_SC16IS7XX namespace
- Fix Kconfig deps
- Keep Kconfig SERIAL_SC16IS7XX_CORE
- Convert to a single Kconfig entry and automatically selects
  I2C and SPI interfaces if available.
- Merge patches 2 and 3
- Add NXP and UART keywords to Kconfig description
- Remove __maybe_unused from of_device_id
- Simplify I2C init/exit with module_i2c_driver()
- Simplify SPI init/exit with module_spi_driver()

Hugo Villeneuve (5):
  serial: sc16is7xx: add proper sched.h include for sched_set_fifo()
  serial: sc16is7xx: unconditionally clear line bit in
    sc16is7xx_remove()
  serial: sc16is7xx: split into core and I2C/SPI parts (core)
  serial: sc16is7xx: split into core and I2C/SPI parts (sc16is7xx_lines)
  serial: sc16is7xx: split into core and I2C/SPI parts
    (sc16is7xx_regcfg)

 drivers/tty/serial/Kconfig         |  47 ++----
 drivers/tty/serial/Makefile        |   2 +
 drivers/tty/serial/sc16is7xx.c     | 261 +++++++----------------------
 drivers/tty/serial/sc16is7xx.h     |  41 +++++
 drivers/tty/serial/sc16is7xx_i2c.c |  67 ++++++++
 drivers/tty/serial/sc16is7xx_spi.c |  90 ++++++++++
 6 files changed, 277 insertions(+), 231 deletions(-)
 create mode 100644 drivers/tty/serial/sc16is7xx.h
 create mode 100644 drivers/tty/serial/sc16is7xx_i2c.c
 create mode 100644 drivers/tty/serial/sc16is7xx_spi.c


base-commit: fec50db7033ea478773b159e0e2efb135270e3b7
-- 
2.39.2