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

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Date: Wed, 22 May 2024 12:08:12 -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 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

> ---
>   drivers/hwmon/ltc2992.c | 11 +++--------
>   1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hwmon/ltc2992.c b/drivers/hwmon/ltc2992.c
> index 229aed15d5ca..3feee400ecf8 100644
> --- a/drivers/hwmon/ltc2992.c
> +++ b/drivers/hwmon/ltc2992.c
> @@ -855,24 +855,19 @@ static const struct regmap_config ltc2992_regmap_config = {
>   static int ltc2992_parse_dt(struct ltc2992_state *st)
>   {
>   	struct fwnode_handle *fwnode;
> -	struct fwnode_handle *child;
>   	u32 addr;
>   	u32 val;
>   	int ret;
>   
>   	fwnode = dev_fwnode(&st->client->dev);
>   
> -	fwnode_for_each_available_child_node(fwnode, child) {
> +	fwnode_for_each_available_child_node_scoped(fwnode, child) {
>   		ret = fwnode_property_read_u32(child, "reg", &addr);
> -		if (ret < 0) {
> -			fwnode_handle_put(child);
> +		if (ret < 0)
>   			return ret;
> -		}
>   
> -		if (addr > 1) {
> -			fwnode_handle_put(child);
> +		if (addr > 1)
>   			return -EINVAL;
> -		}
>   
>   		ret = fwnode_property_read_u32(child, "shunt-resistor-micro-ohms", &val);
>   		if (!ret) {
>