[PATCH v2 00/15] HID: ft260: add UART and GPIO support, plus I2C fixes

[Michael Zaidman <michael.zaidman@gmail.com>]

Mainline supports only the FT260's I2C bridge. This series adds the
UART/TTY interface and GPIO on top of it, and carries the I2C fixes
made alongside them [1].

Patch 1 is Christina Quast's v4 serial driver, ported to the current
I2C code. Patch 2 holds the fixes it needed on hardware. They stay
two patches, as agreed with Jiri, so that each has its own author.
Patches 7 and 8 add flow control and the modem pins.

The v1 thread:
https://lore.kernel.org/all/20260822213941.98882-1-michael.zaidman@gmail.com/T/#t

As said in the v1 thread, this series lands the current driver first.
The MFD split follows as its own series once this one is in the tree.

Changes in v2:

- Patch 1: the UART config enums are split per field and use the
  UART_ infix from the start (Linus Walleij). Lock, read_lock and
  wait are initialised before hid_hw_open(). Lifetime and TTY fixes
  (reported by Sashiko).
- Patch 2: subject now says what it fixes. FT260_UART_RI_DCD_STATUS
  corrected to 0xE2, as in AN_394 section 4.3. 0xB1 length check and
  wake-up timer re-arm (Sashiko).
- Patch 3: subject drops "on top of UART". linux/bits.h, GENMASK()
  and BIT() for the GPIO masks, FT260_GPIO_MAX renamed (Linus
  Walleij). GPIO shadow, combined direction/value report, uart_mode
  OFF (Sashiko).
- Patch 4: timeout of the last I2C read chunk from its length
  (Sashiko).
- Patch 5: a failed feature report is no longer masked; word stores
  use cpu_to_le16() (Sashiko).
- Patch 6: __func__ is printed once (Sashiko).
- Patch 8: v1 patch 10, Rio Liu's RTS/CTS/DTR/DSR polarity fix, is
  folded in, with Co-developed-by. Error paths of tiocmget and
  tiocmset (Sashiko). The TIOCM ioctls stay; the switch to the
  serial_mctrl_gpio helpers needs serial core changes first, as
  discussed with Linus Walleij.
- Patch 9: subject drops "gpio:". i2c_enable moves to the interface
  that owns the gpiochip, so it changes the mask the gpiochip uses.
- Patch 11: the reset work is flushed on unload, and -ENOMEM does not
  trigger a reset (Sashiko).
- Patches 13 to 15 are new: reject an I2C clock outside 60-3400 kHz,
  return the byte count from the i2c_reset store, and recover a bus
  that a slave holds low.

Testing: two FT260 boards, one in chip mode 0x03 with a 24LC512 and
an FT2232 wired to its UART, one with a 24C02. A pytest suite of 202
tests [2] drives sysfs, the gpiochip, the I2C adapter and the tty. It
ran on 7.3.0-rc4 with this series applied, built with PROVE_LOCKING
and DEBUG_ATOMIC_SLEEP, loading the in-tree module. The second board
was strapped to 0x00, 0x01 and 0x02 in turn; each of the 202 tests
passed in at least one of the three runs, with no lockdep report.
Every patch builds with W=1 without warnings.
checkpatch --strict reports no errors and one warning, for a quoted
kernel log line in patch 15.

[1] https://github.com/MichaelZaidman/hid-ft260
[2] https://github.com/MichaelZaidman/hid-ft260/tree/main/tests

Christina Quast (1):
  HID: ft260: add serial driver

Michael Zaidman (14):
  HID: ft260: uart: fix the serial driver
  HID: ft260: add GPIO support
  HID: ft260: i2c: reduce driver module loading time
  HID: ft260: i2c: silence sysfs store big-numbers
  HID: ft260: i2c: reduce bus-error message severity
  HID: ft260: uart: enable flow control
  HID: ft260: uart: add modem pins control via ioctl
  HID: ft260: group sysfs attrs per HID interface
  HID: ft260: i2c: fix large write transaction failure
  HID: ft260: workaround for TN_189 errata endpoint STALL after
    enumeration
  HID: ft260: i2c: abort in-flight transfers with STOP before reset
  HID: ft260: i2c: reject an I2C clock outside the supported range
  HID: ft260: i2c: fix i2c_reset sysfs store return value
  HID: ft260: i2c: recover a bus held by a slave

 drivers/hid/Kconfig     |   10 +-
 drivers/hid/hid-ft260.c | 2435 ++++++++++++++++++++++++++++++++++-----
 2 files changed, 2175 insertions(+), 270 deletions(-)


base-commit: 720806515cb6921ab05caaa6f470f7054b56385e
-- 
2.43.0