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: <CAGXv+5EJvy6KwJZWCUTNQiec03WdB9m-XeEp4yicxD8FuWVrMQ@mail.gmail.com>
Date: Mon, 14 Oct 2024 16:24:48 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
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, Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v4 2/6] thermal: of: Use scoped memory and OF handling to
 simplify thermal_of_trips_init()

On Fri, Oct 11, 2024 at 2:06 AM 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>
> ---
>
> 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).

The additional changes are the same as what I had done, except that
I used "return_ptr(tt)" instead of "return no_free_ptr(tt)", and I
had reset *ntrips to 0 at the beginning.

So,

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

> 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);
> +       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)
>
> --
> 2.43.0
>