Re: [PATCH v3 1/3] leds: triggers: provide led_trigger_register_format()

[Jacek Anaszewski <jacek.anaszewski@gmail.com>]

Hi Uwe,

Thank you for the patch. It looks fine, but please split
the drivers/net/can/led.c related changes into a separate one.

Best regards,
Jacek Anaszewski

On 05/08/2018 12:05 PM, Uwe Kleine-König wrote:
> This allows one to simplify drivers that provide a trigger with a
> non-constant name (e.g. one trigger per device with the trigger name
> depending on the device's name).
> 
> Internally the memory the name member of struct led_trigger points to
> now always allocated dynamically instead of just taken from the caller.
> 
> The function led_trigger_rename_static() must be changed accordingly and
> was renamed to led_trigger_rename() for consistency, with the only user
> adapted.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>   drivers/leds/led-triggers.c | 84 +++++++++++++++++++++++++++----------
>   drivers/net/can/led.c       |  6 +--
>   include/linux/leds.h        | 30 +++++++------
>   3 files changed, 81 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 431123b048a2..5d8bb504b07b 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -175,18 +175,34 @@ void led_trigger_set_default(struct led_classdev *led_cdev)
>   }
>   EXPORT_SYMBOL_GPL(led_trigger_set_default);
>   
> -void led_trigger_rename_static(const char *name, struct led_trigger *trig)
> +int led_trigger_rename(struct led_trigger *trig, const char *fmt, ...)
>   {
> -	/* new name must be on a temporary string to prevent races */
> -	BUG_ON(name == trig->name);
> +	const char *prevname;
> +	const char *newname;
> +	va_list args;
> +
> +	if (!trig)
> +		return 0;
> +
> +	va_start(args, fmt);
> +	newname = kvasprintf_const(GFP_KERNEL, fmt, args);
> +	va_end(args);
> +
> +	if (!newname) {
> +		pr_err("Failed to allocate new name for trigger %s\n", trig->name);
> +		return -ENOMEM;
> +	}
>   
>   	down_write(&triggers_list_lock);
> -	/* this assumes that trig->name was originaly allocated to
> -	 * non constant storage */
> -	strcpy((char *)trig->name, name);
> +	prevname = trig->name;
> +	trig->name = newname;
>   	up_write(&triggers_list_lock);
> +
> +	kfree_const(prevname);
> +
> +	return 0;
>   }
> -EXPORT_SYMBOL_GPL(led_trigger_rename_static);
> +EXPORT_SYMBOL_GPL(led_trigger_rename);
>   
>   /* LED Trigger Interface */
>   
> @@ -333,34 +349,56 @@ void led_trigger_blink_oneshot(struct led_trigger *trig,
>   }
>   EXPORT_SYMBOL_GPL(led_trigger_blink_oneshot);
>   
> -void led_trigger_register_simple(const char *name, struct led_trigger **tp)
> +int led_trigger_register_format(struct led_trigger **tp, const char *fmt, ...)
>   {
> +	va_list args;
>   	struct led_trigger *trig;
> -	int err;
> +	int err = -ENOMEM;
> +	const char *name;
> +
> +	va_start(args, fmt);
> +	name = kvasprintf_const(GFP_KERNEL, fmt, args);
> +	va_end(args);
>   
>   	trig = kzalloc(sizeof(struct led_trigger), GFP_KERNEL);
>   
> -	if (trig) {
> -		trig->name = name;
> -		err = led_trigger_register(trig);
> -		if (err < 0) {
> -			kfree(trig);
> -			trig = NULL;
> -			pr_warn("LED trigger %s failed to register (%d)\n",
> -				name, err);
> -		}
> -	} else {
> -		pr_warn("LED trigger %s failed to register (no memory)\n",
> -			name);
> -	}
> +	if (!name || !trig)
> +		goto err;
> +
> +	trig->name = name;
> +
> +	err = led_trigger_register(trig);
> +	if (err < 0)
> +		goto err;
> +
>   	*tp = trig;
> +
> +	return 0;
> +
> +err:
> +	kfree(trig);
> +	kfree_const(name);
> +
> +	*tp = NULL;
> +
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(led_trigger_register_format);
> +
> +void led_trigger_register_simple(const char *name, struct led_trigger **tp)
> +{
> +	int ret = led_trigger_register_format(tp, "%s", name);
> +	if (ret < 0)
> +		pr_warn("LED trigger %s failed to register (%d)\n", name, ret);
>   }
>   EXPORT_SYMBOL_GPL(led_trigger_register_simple);
>   
>   void led_trigger_unregister_simple(struct led_trigger *trig)
>   {
> -	if (trig)
> +	if (trig) {
>   		led_trigger_unregister(trig);
> +		kfree_const(trig->name);
> +	}
>   	kfree(trig);
>   }
>   EXPORT_SYMBOL_GPL(led_trigger_unregister_simple);
> diff --git a/drivers/net/can/led.c b/drivers/net/can/led.c
> index c1b667675fa1..2d7d1b0d20f9 100644
> --- a/drivers/net/can/led.c
> +++ b/drivers/net/can/led.c
> @@ -115,13 +115,13 @@ static int can_led_notifier(struct notifier_block *nb, unsigned long msg,
>   
>   	if (msg == NETDEV_CHANGENAME) {
>   		snprintf(name, sizeof(name), "%s-tx", netdev->name);
> -		led_trigger_rename_static(name, priv->tx_led_trig);
> +		led_trigger_rename(priv->tx_led_trig, name);
>   
>   		snprintf(name, sizeof(name), "%s-rx", netdev->name);
> -		led_trigger_rename_static(name, priv->rx_led_trig);
> +		led_trigger_rename(priv->rx_led_trig, name);
>   
>   		snprintf(name, sizeof(name), "%s-rxtx", netdev->name);
> -		led_trigger_rename_static(name, priv->rxtx_led_trig);
> +		led_trigger_rename(priv->rxtx_led_trig, name);
>   	}
>   
>   	return NOTIFY_DONE;
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index b7e82550e655..e706c28bb35b 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -275,6 +275,8 @@ extern void led_trigger_unregister(struct led_trigger *trigger);
>   extern int devm_led_trigger_register(struct device *dev,
>   				     struct led_trigger *trigger);
>   
> +extern int led_trigger_register_format(struct led_trigger **trigger,
> +				       const char *fmt, ...);
>   extern void led_trigger_register_simple(const char *name,
>   				struct led_trigger **trigger);
>   extern void led_trigger_unregister_simple(struct led_trigger *trigger);
> @@ -298,28 +300,25 @@ static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
>   }
>   
>   /**
> - * led_trigger_rename_static - rename a trigger
> - * @name: the new trigger name
> + * led_trigger_rename - rename a trigger
>    * @trig: the LED trigger to rename
> + * @fmt: format string for new name
>    *
> - * Change a LED trigger name by copying the string passed in
> - * name into current trigger name, which MUST be large
> - * enough for the new string.
> - *
> - * Note that name must NOT point to the same string used
> - * during LED registration, as that could lead to races.
> - *
> - * This is meant to be used on triggers with statically
> - * allocated name.
> + * rebaptize the given trigger.
>    */
> -extern void led_trigger_rename_static(const char *name,
> -				      struct led_trigger *trig);
> +extern int led_trigger_rename(struct led_trigger *trig, const char *fmt, ...);
>   
>   #else
>   
>   /* Trigger has no members */
>   struct led_trigger {};
>   
> +static inline int led_trigger_register_format(struct led_trigger **trigger,
> +					      const char *fmt, ...)
> +{
> +	return 0;
> +}
> +
>   /* Trigger inline empty functions */
>   static inline void led_trigger_register_simple(const char *name,
>   					struct led_trigger **trigger) {}
> @@ -342,6 +341,11 @@ static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
>   	return NULL;
>   }
>   
> +static inline int led_trigger_rename(struct led_trigger *trig, const char *fmt, ...)
> +{
> +	return 0;
> +}
> +
>   #endif /* CONFIG_LEDS_TRIGGERS */
>   
>   /* Trigger specific functions */
>