auxdisplay: ht16k33: Drop device node reference after registration failure in ht16k33_led_probe()

[PATCH] auxdisplay: ht16k33: Drop device node reference after registration failure in ht16k33_led_probe()

Posted by Markus Elfring 1 year, 8 months ago

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Tue, 4 Jun 2024 17:02:15 +0200

A failed call of the function “devm_led_classdev_register_ext”
can be reported.
Add a call of the function “fwnode_handle_put” for this error case.

Fixes: c223d9c636ed ("auxdisplay: ht16k33: Add LED support")
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 drivers/auxdisplay/ht16k33.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
index ce987944662c..ef86537c9d83 100644
--- a/drivers/auxdisplay/ht16k33.c
+++ b/drivers/auxdisplay/ht16k33.c
@@ -483,8 +483,10 @@ static int ht16k33_led_probe(struct device *dev, struct led_classdev *led,
 	led->max_brightness = MAX_BRIGHTNESS;

 	err = devm_led_classdev_register_ext(dev, led, &init_data);
-	if (err)
+	if (err) {
 		dev_err(dev, "Failed to register LED\n");
+		fwnode_handle_put(init_data.fwnode);
+	}

 	return err;
 }
--
2.45.1

Re: [PATCH] auxdisplay: ht16k33: Drop device node reference after registration failure in ht16k33_led_probe()

Posted by Andy Shevchenko 1 year, 8 months ago

On Tue, Jun 04, 2024 at 05:15:37PM +0200, Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Tue, 4 Jun 2024 17:02:15 +0200
> 
> A failed call of the function “devm_led_classdev_register_ext”
> can be reported.
> Add a call of the function “fwnode_handle_put” for this error case.

Replace double quotes by parentheses, so the reference to the functions
will look like func().

...

>  	err = devm_led_classdev_register_ext(dev, led, &init_data);
> -	if (err)
> +	if (err) {
>  		dev_err(dev, "Failed to register LED\n");
> +		fwnode_handle_put(init_data.fwnode);
> +	}

There are two issues with this approach:
1) there is the same issue in ->remove(), isn't it?
2) it potentially might mess up the ordering if any other devm call happens
   in beetween.

But, by design we don't use reference counting after we registered LED, hence
both error and successful paths need to have this, so add another
fwnode_handle_put() after this branch.

-- 
With Best Regards,
Andy Shevchenko

Re: auxdisplay: ht16k33: Drop device node reference after registration failure in ht16k33_led_probe()

Posted by Markus Elfring 1 year, 8 months ago

> But, by design we don't use reference counting after we registered LED,
> hence both error and successful paths need to have this,

Do you indicate really special data processing constraints here?


> so add another fwnode_handle_put() after this branch.

Will this suggestion trigger any further clarifications for the affected software?

Regards,
Markus