linux-kernel - Re: [PATCH v2][next] tty: sunsu: Simplify device_node cleanup by using _

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Date: Thu, 2 May 2024 19:05:03 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Shresth Prasad <shresthprasad7@...il.com>
cc: davem@...emloft.net, gregkh@...uxfoundation.org, jirislaby@...nel.org, 
    sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org, 
    linux-serial@...r.kernel.org, javier.carrasco.cruz@...il.com, 
    skhan@...uxfoundation.org, Julia Lawall <julia.lawall@...ia.fr>
Subject: Re: [PATCH v2][next] tty: sunsu: Simplify device_node cleanup by
 using __free

On Wed, 1 May 2024, Shresth Prasad wrote:

> Add `__free` function attribute to `ap` and `match` pointer
> initialisations which ensure that the pointers are freed as soon as they
> go out of scope, thus removing the need to manually free them using
> `of_node_put`.
> 
> This also removes the need for the `goto` statement and the `rc`
> variable.
> 
> Tested using a qemu x86_64 virtual machine.

Eh, how can you test this with an x86_64 VM ???

config SERIAL_SUNSU
        tristate "Sun SU serial support"
        depends on SPARC && PCI

-- 
 i.


> Suggested-by: Julia Lawall <julia.lawall@...ia.fr>
> Signed-off-by: Shresth Prasad <shresthprasad7@...il.com>
> ---
> Changes in v2:
>     - Specify how the patch was tested
> 
>  drivers/tty/serial/sunsu.c | 37 +++++++++++--------------------------
>  1 file changed, 11 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/tty/serial/sunsu.c b/drivers/tty/serial/sunsu.c
> index 67a5fc70bb4b..0f463da5e7ce 100644
> --- a/drivers/tty/serial/sunsu.c
> +++ b/drivers/tty/serial/sunsu.c
> @@ -1382,44 +1382,29 @@ static inline struct console *SUNSU_CONSOLE(void)
>  
>  static enum su_type su_get_type(struct device_node *dp)
>  {
> -	struct device_node *ap = of_find_node_by_path("/aliases");
> -	enum su_type rc = SU_PORT_PORT;
> +	struct device_node *ap __free(device_node) =
> +			    of_find_node_by_path("/aliases");
>  
>  	if (ap) {
>  		const char *keyb = of_get_property(ap, "keyboard", NULL);
>  		const char *ms = of_get_property(ap, "mouse", NULL);
> -		struct device_node *match;
>  
>  		if (keyb) {
> -			match = of_find_node_by_path(keyb);
> +			struct device_node *match __free(device_node) =
> +					    of_find_node_by_path(keyb);
>  
> -			/*
> -			 * The pointer is used as an identifier not
> -			 * as a pointer, we can drop the refcount on
> -			 * the of__node immediately after getting it.
> -			 */
> -			of_node_put(match);
> -
> -			if (dp == match) {
> -				rc = SU_PORT_KBD;
> -				goto out;
> -			}
> +			if (dp == match)
> +				return SU_PORT_KBD;
>  		}
>  		if (ms) {
> -			match = of_find_node_by_path(ms);
> +			struct device_node *match __free(device_node) =
> +					    of_find_node_by_path(ms);
>  
> -			of_node_put(match);
> -
> -			if (dp == match) {
> -				rc = SU_PORT_MS;
> -				goto out;
> -			}
> +			if (dp == match)
> +				return SU_PORT_MS;
>  		}
>  	}
> -
> -out:
> -	of_node_put(ap);
> -	return rc;
> +	return SU_PORT_PORT;
>  }
>  
>  static int su_probe(struct platform_device *op)
>