hwmon: (nct7904) serialise the watchdog and sensors

The registers of the chip are banked: each access selects the bank, which
is cached in data->bank_sel, and then reads or writes the register.
bank_lock used to make the two steps atomic.  It has been removed because
the hwmon core serialises the sensor callbacks, but the watchdog callbacks
use the same access functions and are not called by the hwmon core.

So a sensor can now be read while the watchdog is being pinged.  If one of
them selects its bank between the two steps of the other, the second step
hits a register of the wrong bank: the watchdog is not fed, or its
commands are written to some sensor or fan control register.

Take the lock of the hwmon device in the watchdog callbacks.  The watchdog
is registered after the hwmon device, and devres unregisters it first.

Fixes: 9ad270bf4dcc ("hwmon: (nct7904) Rely on subsystem locking")
Assisted-by: LLM
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

0 files changed, 0 insertions, 0 deletions