thermal: core: Save a few bytes of memory when registering a cooling device

Some *thermal_cooling_device_register() calls pass a string literal as the
'type' parameter.

So kstrdup_const() can be used instead of kfree() to avoid a memory
allocation in such cases.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/thermal/thermal_core.c | 6 +++---
 include/linux/thermal.h        | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

On Fri, Jan 5, 2024 at 2:45 PM Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>
> Some *thermal_cooling_device_register() calls pass a string literal as the
> 'type' parameter.
>
> So kstrdup_const() can be used instead of kfree() to avoid a memory
> allocation in such cases.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  drivers/thermal/thermal_core.c | 6 +++---
>  include/linux/thermal.h        | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index fa88d8707241..d21225ddbf10 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -846,7 +846,7 @@ static void thermal_release(struct device *dev)
>                             sizeof("cooling_device") - 1)) {
>                 cdev = to_cooling_device(dev);
>                 thermal_cooling_device_destroy_sysfs(cdev);
> -               kfree(cdev->type);
> +               kfree_const(cdev->type);
>                 ida_free(&thermal_cdev_ida, cdev->id);
>                 kfree(cdev);
>         }
> @@ -918,7 +918,7 @@ __thermal_cooling_device_register(struct device_node *np,
>         cdev->id = ret;
>         id = ret;
>
> -       cdev->type = kstrdup(type ? type : "", GFP_KERNEL);
> +       cdev->type = kstrdup_const(type ? type : "", GFP_KERNEL);
>         if (!cdev->type) {
>                 ret = -ENOMEM;
>                 goto out_ida_remove;
> @@ -969,7 +969,7 @@ __thermal_cooling_device_register(struct device_node *np,
>  out_cooling_dev:
>         thermal_cooling_device_destroy_sysfs(cdev);
>  out_cdev_type:
> -       kfree(cdev->type);
> +       kfree_const(cdev->type);
>  out_ida_remove:
>         ida_free(&thermal_cdev_ida, id);
>  out_kfree_cdev:
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index bf84595a4e86..052c72c0fa17 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -102,7 +102,7 @@ struct thermal_cooling_device_ops {
>
>  struct thermal_cooling_device {
>         int id;
> -       char *type;
> +       const char *type;
>         unsigned long max_state;
>         struct device device;
>         struct device_node *np;
> --

Applied as 6.8-rc1 material under a different subject and with some
changelog edits.

Thanks!