Fan control does not work on an ASRock B850 Steel Legend WiFi (NCT6686D,
EC firmware 1.0 build 10/29/24). The driver does not recognise the board's
customer ID, so it only probes with force=1. Its pwm attributes are then
read-only, and even once writable the EC ignores them until the fan is put
in manual mode through register 0xa00, which the driver does not expose.
Writes that do get through are sometimes silently discarded, because the
settling delay in store_pwm() is too short on this firmware.

This series fixes those one at a time. Patch 1 stands on its own: a write
that succeeds on the first attempt issues the same register sequence as
today, so boards that work now are unaffected. The fan control changes are
exposed on verified boards only.

With the whole series applied, all six fans report and pwm[1-6]_enable read
2 after probe:

  fan1: 815 RPM   fan2: 631 RPM   fan5: 386 RPM   fan6: 354 RPM

With pwm5 in manual mode:

  written   applied   fan5
  60        60        337 RPM
  100       100       443 RPM
  150       150       627 RPM
  200       200       794 RPM
  255       255       933 RPM

Writing 2 back returns the fan to the EC, as does unloading the driver.
Without patch 1, two of six writes were lost and the fan kept following its
previous value.

Each patch was also built individually. I have no access to Mitac, MSI or
Intel hardware.

Johan Dahlin (5):
  hwmon: (nct6683) Retry pwm writes until they take effect
  hwmon: (nct6683) Add customer ID for ASRock B850 Steel Legend WiFi
  hwmon: (nct6683) Add pwm[1-8]_enable
  hwmon: (nct6683) Restore fan control mode on driver removal
  hwmon: (nct6683) Enable pwm control on ASRock B850 Steel Legend WiFi

 Documentation/hwmon/nct6683.rst |   7 ++
 drivers/hwmon/nct6683.c         | 124 +++++++++++++++++++++++++++++---
 2 files changed, 122 insertions(+), 9 deletions(-)

-- 
2.53.0