linux-kernel - Re: [PATCH v4 2/6] thermal: of: Use scoped memory and OF handling to simplify thermal_of_trips

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Message-ID: <20241016145851.00004e90@Huawei.com>
Date: Wed, 16 Oct 2024 14:58:51 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC: "Rafael J. Wysocki" <rafael@...nel.org>, Daniel Lezcano
	<daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, Lukasz Luba
	<lukasz.luba@....com>, Amit Kucheria <amitk@...nel.org>, Thara Gopinath
	<thara.gopinath@...il.com>, Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>, Vasily Khoruzhick
	<anarsoul@...il.com>, Yangtao Li <tiny.windzz@...il.com>, Chen-Yu Tsai
	<wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland
	<samuel@...lland.org>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
	<linux-tegra@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-sunxi@...ts.linux.dev>, Chen-Yu Tsai <wenst@...omium.org>
Subject: Re: [PATCH v4 2/6] thermal: of: Use scoped memory and OF handling
 to simplify thermal_of_trips_init()

On Thu, 10 Oct 2024 20:06:18 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> Obtain the device node reference and allocate memory with
> scoped/cleanup.h to reduce error handling and make the code a bit
> simpler.
> 
> The code is not equivalent in one minor aspect: outgoing parameter
> "*ntrips" will not be zeroed on errors of memory allocation.  This
> difference is not important, because code was already not zeroing it in
> case of earlier errors and the only caller does not rely on ntrips being
> 0 in case of errors.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Trivial unrelated comment inline + maybe return_ptr() is the way to go as
Chen-Yu mentioned.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
> 
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Cc: Chen-Yu Tsai <wenst@...omium.org>
> 
> Changes in v4:
> 1. Significant change: kzalloc() also with scoped-handling so the entire
>    error handling could be removed.
> 2. Due to above, drop review-tags (Chen-Yu, Jonathan).
> 
> Changes in v2:
> 1. Drop left-over of_node_put in regular exit path (Chen-Yu)
> ---
>  drivers/thermal/thermal_of.c | 31 ++++++++-----------------------
>  1 file changed, 8 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
> index f0ffc0e335ba9406f4fd858d6c561f9d23f4b842..37db435b54b124abf25b1d75d6cc4fb75f1c1e5c 100644
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -95,11 +95,9 @@ static int thermal_of_populate_trip(struct device_node *np,
>  
>  static struct thermal_trip *thermal_of_trips_init(struct device_node *np, int *ntrips)
>  {
> -	struct thermal_trip *tt;
> -	struct device_node *trips;
>  	int ret, count;
>  
> -	trips = of_get_child_by_name(np, "trips");
> +	struct device_node *trips __free(device_node) = of_get_child_by_name(np, "trips");
>  	if (!trips) {
>  		pr_err("Failed to find 'trips' node\n");
>  		return ERR_PTR(-EINVAL);
> @@ -108,36 +106,23 @@ static struct thermal_trip *thermal_of_trips_init(struct device_node *np, int *n
>  	count = of_get_child_count(trips);
>  	if (!count) {
>  		pr_err("No trip point defined\n");
> -		ret = -EINVAL;
> -		goto out_of_node_put;
> +		return ERR_PTR(-EINVAL);
>  	}
>  
> -	tt = kzalloc(sizeof(*tt) * count, GFP_KERNEL);
> -	if (!tt) {
> -		ret = -ENOMEM;
> -		goto out_of_node_put;
> -	}
> -
> -	*ntrips = count;
> +	struct thermal_trip *tt __free(kfree) = kzalloc(sizeof(*tt) * count, GFP_KERNEL);

Trivial and unrelated, but maybe kcalloc(count, sizeof(tt), GFP_KERNEL);

> +	if (!tt)
> +		return ERR_PTR(-ENOMEM);
>  
>  	count = 0;
>  	for_each_child_of_node_scoped(trips, trip) {
>  		ret = thermal_of_populate_trip(trip, &tt[count++]);
>  		if (ret)
> -			goto out_kfree;
> +			return ERR_PTR(ret);
>  	}
>  
> -	of_node_put(trips);
> +	*ntrips = count;
>  
> -	return tt;
> -
> -out_kfree:
> -	kfree(tt);
> -	*ntrips = 0;
> -out_of_node_put:
> -	of_node_put(trips);
> -
> -	return ERR_PTR(ret);
> +	return no_free_ptr(tt);
>  }
>  
>  static struct device_node *of_thermal_zone_find(struct device_node *sensor, int id)
>