Patch "thermal: core: Do not fail cdev registration because of invalid initial state" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    thermal: core: Do not fail cdev registration because of invalid initial state

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     thermal-core-do-not-fail-cdev-registration-because-o.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 81b1cc7ba4999d1a369184ed8a0c03a72b4f9372
Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Date:   Thu Jun 6 20:27:19 2024 +0200

    thermal: core: Do not fail cdev registration because of invalid initial state
    
    [ Upstream commit 1af89dedc8a58006d8e385b1e0d2cd24df8a3b69 ]
    
    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@xxxxxxxxxxxxx
    Reported-by: Laura Nao <laura.nao@xxxxxxxxxxxxx>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
    Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
    Tested-by: Laura Nao <laura.nao@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 38b7d02384d7c..258482036f1e9 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -936,9 +936,17 @@ __thermal_cooling_device_register(struct device_node *np,
 	if (ret)
 		goto out_cdev_type;
 
+	/*
+	 * The cooling device's current state is only needed for debug
+	 * initialization below, so a failure to get it does not cause
+	 * the entire cooling device initialization to fail.  However,
+	 * the debug will not work for the device if its initial state
+	 * cannot be determined and drivers are responsible for ensuring
+	 * that this will not happen.
+	 */
 	ret = cdev->ops->get_cur_state(cdev, &current_state);
 	if (ret)
-		goto out_cdev_type;
+		current_state = ULONG_MAX;
 
 	thermal_cooling_device_setup_sysfs(cdev);
 
@@ -953,7 +961,8 @@ __thermal_cooling_device_register(struct device_node *np,
 		return ERR_PTR(ret);
 	}
 
-	thermal_debug_cdev_add(cdev, current_state);
+	if (current_state <= cdev->max_state)
+		thermal_debug_cdev_add(cdev, current_state);
 
 	/* Add 'this' new cdev to the global cdev list */
 	mutex_lock(&thermal_list_lock);