Re: [PATCH v3] thermal: core: Do not fail cdev registration because of invalid initial state

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 06/06/2024 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>
> ---

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

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