Re: [PATCH v3] thermal: core: Do not fail cdev registration

[Laura Nao <laura.nao@collabora.com>]

On 6/6/24 20:14, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Subject: [PATCH v3] thermal: core: Do not fail cdev registration
> because of invalid initial state
> 
> It is reported that commit 31a0fa0019b0 ("thermal/debugfs: Pass
> cooling
> device state to thermal_debug_cdev_add()") causes the ACPI fan driver
> to fail probing on some systems which turns out to be due to the _FST
> control method returning an invalid value until _FSL is first
> evaluated
> for the given fan.  If this happens, the .get_cur_state() cooling
> device
> callback returns an error and __thermal_cooling_device_register()
> fails
> as uses that callback after commit 31a0fa0019b0.
> 
> Arguably, _FST should not return an invalid value even if it is
> evaluated before _FSL, so this may be regarded as a platform firmware
> issue, but at the same time it is not a good enough reason for failing
> the cooling device registration where the initial cooling device state
> is only needed to initialize a thermal debug facility.
> 
> Accordingly, modify __thermal_cooling_device_register() to avoid
> calling thermal_debug_cdev_add() instead of returning an error if the
> initial .get_cur_state() callback invocation fails.
> 
> Fixes: 31a0fa0019b0 ("thermal/debugfs: Pass cooling device state to
> thermal_debug_cdev_add()")
> Closes:
> https://lore.kernel.org/linux-acpi/20240530153727.843378-1-laura.nao@collabora.com
> Reported-by: Laura Nao <laura.nao@collabora.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---

Tested-by: Laura Nao <laura.nao@collabora.com>

Thanks,

Laura