[PATCH 0/9] serial: add new I/O type for SPI and I2C bus devices

[Hugo Villeneuve <hugo@hugovil.com>]

Hello,
this patch series add a new I/O type for serial devices on a SPI/I2C bus.

These changes are based on a suggestion [1] made by Ilpo Järvinen during
past sc16is7xx driver patches review.

I decided to use UPIO_BUS/SERIAL_IO_BUS names but maybe other names would
be more appropriate:
   UPIO_SBUS   / SERIAL_IO_SBUS
   UPIO_SERBUS / SERIAL_IO_SERBUS
   UPIO_EXT    / SERIAL_IO_EXT
   UPIO_CUSTOM / SERIAL_IO_CUSTOM
   UPIO_REGMAP / SERIAL_IO_REGMAP  /* Maybe not always true in future? */
   ...

Tested on a imx6 board with two SC16is752 using SPI mode, and a dummy
device-tree entry for a MAX3100:
  dmesg -t | grep "base_baud"
    2020000.serial: ttymxc0 at MMIO 0x2020000 (irq = 197, base_baud = 5000000) is a IMX
    21e8000.serial: ttymxc1 at MMIO 0x21e8000 (irq = 198, base_baud = 5000000) is a IMX
    spi1.0: ttySC0 (irq = 165, base_baud = 1500000) is a SC16IS752
    spi1.0: ttySC1 (irq = 165, base_baud = 1500000) is a SC16IS752
    spi3.0: ttySC2 (irq = 37, base_baud = 1500000) is a SC16IS752
    spi3.0: ttySC3 (irq = 37, base_baud = 1500000) is a SC16IS752
    spi3.1: ttyMAX0 (irq = 0, base_baud = 0) is a MAX3100
Note that before these patches, max3100 silently failed in uart_configure_port()
because membase/iobase/mapbase were zero.

For max310x and SC16is7xx in i2c mode, tested only that driver is properly
registered by using i2c-stub.

Also tested on a custom board with a Renesas RZ/G2L cpu (sh-sci driver) to
confirm there is no regression:
  dmesg -t | grep "base_baud"
    1004b800.serial: ttySC0 at MMIO 0x1004b800 (irq = 35, base_baud = 0) is a scif
    1004bc00.serial: ttySC1 at MMIO 0x1004bc00 (irq = 40, base_baud = 0) is a scif

Maybe some of the patches could be merged together, but for now I decided
to keep them separate to help the review process.

Thank you.

[1] https://lore.kernel.org/lkml/2936e18f-44ea-faed-9fa0-2ddefe7c3194@linux.intel.com/raw

---
Hugo Villeneuve (9):
      serial: core: add uart_iotype_mmio/legacy_io helper functions
      serial: core: use uart_iotype_*() to simplify code
      serial: 8250: use uart_iotype_*() to simplify code
      serial: core: fix indentation/alignment
      serial: core: add new I/O type for SPI and I2C bus devices
      serial: core: prevent irrelevant I/O infos display for UPIO_BUS
      serial: sc16is7xx: use new UPIO_BUS as iotype
      serial: max310x: use new UPIO_BUS as iotype
      serial: max3100: use new UPIO_BUS as iotype

 drivers/tty/serial/8250/8250_port.c |  33 ++--------
 drivers/tty/serial/max3100.c        |   1 +
 drivers/tty/serial/max310x.c        |   9 +--
 drivers/tty/serial/sc16is7xx.c      |   9 +--
 drivers/tty/serial/serial_core.c    | 121 ++++++++++++++++++++----------------
 include/linux/serial_core.h         |   5 ++
 include/uapi/linux/serial.h         |   1 +
 7 files changed, 83 insertions(+), 96 deletions(-)
---
base-commit: 2e68039281932e6dc37718a1ea7cbb8e2cda42e6
change-id: 20260423-tty-upio-c8b66a0a593e

Best regards,
-- 
Hugo Villeneuve <hvilleneuve@dimonoff.com>