linux-kernel - Re: [PATCH 2/2] hwmon: (ltc2992) use fwnode_for_each_available_child_node

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Message-ID: <aab6fafe-e7b3-4ee0-beb3-2eaca9d1a1ed@roeck-us.net>
Date: Wed, 22 May 2024 15:51:08 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Daniel Scally <djrscally@...il.com>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>, Jean Delvare
 <jdelvare@...e.com>, Antoniu Miclaus <antoniu.miclaus@...log.com>,
 Jonathan Cameron <jic23@...nel.org>
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hwmon@...r.kernel.org
Subject: Re: [PATCH 2/2] hwmon: (ltc2992) use
 fwnode_for_each_available_child_node_scoped()

On 5/22/24 12:46, Javier Carrasco wrote:
> On 22/05/2024 21:08, Guenter Roeck wrote:
>> On 5/22/24 02:18, Javier Carrasco wrote:
>>> The error path from a zero value of the "shunt-resistor-micro-ohms"
>>> property does not decrement the refcount of the child node.
>>>
>>> Instead of adding the missing fwnode_handle_put(), a safer fix for
>>> future modifications is using the _scoped version of the macro,
>>> which removes the need for fwnode_handle_put() in all error paths.
>>>
>>> The macro defines the child node internally, which removes the need for
>>> the current child node declaration as well.
>>>
>>> Fixes: 10b029020487 ("hwmon: (ltc2992) Avoid division by zero")
>>> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
>>
>> I really don't like fixes which depend on an API change.
>>
>> Guenter
>>
> 
> We could split the fix into two steps as suggested by Andy, where the
> fix would simply add the missing fwnode_handle_put(), adding the
> corresponding tag to include it in the stable kernels (the bug was
> introduced with v6.7). By doing that, the new macro would not need to be
> backported, which is probably a safer approach.
> 
> The patch with the new macro would be left as it is, and another patch
> would convert the the loop to use the new macro to avoid that a similar
> bug arises again. That would be this 2/2 + dropping the additional
> fwnode_handle_put().
> 

Please do.

Thanks,
Guenter

> Best regards,
> Javier Carrasco
>