Patch "platform: Provide a remove callback that returns no value" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    platform: Provide a remove callback that returns no value

to the 5.10-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:
     platform-provide-a-remove-callback-that-returns-no-v.patch
and it can be found in the queue-5.10 subdirectory.

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



commit 6f4946eef20eaaf56aeb2414f4626249a8f4679a
Author: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Date:   Fri Dec 9 16:09:14 2022 +0100

    platform: Provide a remove callback that returns no value
    
    [ Upstream commit 5c5a7680e67ba6fbbb5f4d79fa41485450c1985c ]
    
    struct platform_driver::remove returning an integer made driver authors
    expect that returning an error code was proper error handling. However
    the driver core ignores the error and continues to remove the device
    because there is nothing the core could do anyhow and reentering the
    remove callback again is only calling for trouble.
    
    So this is an source for errors typically yielding resource leaks in the
    error path.
    
    As there are too many platform drivers to neatly convert them all to
    return void in a single go, do it in several steps after this patch:
    
     a) Convert all drivers to implement .remove_new() returning void instead
        of .remove() returning int;
     b) Change struct platform_driver::remove() to return void and so make
        it identical to .remove_new();
     c) Change all drivers back to .remove() now with the better prototype;
     d) drop struct platform_driver::remove_new().
    
    While this touches all drivers eventually twice, steps a) and c) can be
    done one driver after another and so reduces coordination efforts
    immensely and simplifies review.
    
    Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20221209150914.3557650-1-u.kleine-koenig@xxxxxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Stable-dep-of: 55c421b36448 ("mmc: davinci: Don't strip remove function when driver is builtin")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index d0b15cbab0ff0..e07043d85c65c 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1306,7 +1306,9 @@ static int platform_remove(struct device *_dev)
 	struct platform_driver *drv = to_platform_driver(_dev->driver);
 	struct platform_device *dev = to_platform_device(_dev);
 
-	if (drv->remove) {
+	if (drv->remove_new) {
+		drv->remove_new(dev);
+	} else if (drv->remove) {
 		int ret = drv->remove(dev);
 
 		if (ret)
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index e7a83b0218077..870a918aa251c 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -203,7 +203,18 @@ extern void platform_device_put(struct platform_device *pdev);
 
 struct platform_driver {
 	int (*probe)(struct platform_device *);
+
+	/*
+	 * Traditionally the remove callback returned an int which however is
+	 * ignored by the driver core. This led to wrong expectations by driver
+	 * authors who thought returning an error code was a valid error
+	 * handling strategy. To convert to a callback returning void, new
+	 * drivers should implement .remove_new() until the conversion it done
+	 * that eventually makes .remove() return void.
+	 */
 	int (*remove)(struct platform_device *);
+	void (*remove_new)(struct platform_device *);
+
 	void (*shutdown)(struct platform_device *);
 	int (*suspend)(struct platform_device *, pm_message_t state);
 	int (*resume)(struct platform_device *);