Re: [PATCH 11/15] rfkill: add notifier chains support

[Ivo van Doorn <ivdoorn@gmail.com>]

On Sunday 18 May 2008, Henrique de Moraes Holschuh wrote:
> Add a notifier chain for use by the rfkill class.  This notifier chain
> signals the following events (more to be added when needed):
> 
>   1. rfkill: rfkill device state has changed
> 
> A pointer to the rfkill struct will be passed as a parameter.
> 
> The notifier message types have been added to include/linux/rfkill.h
> instead of to include/linux/notifier.h in order to avoid the madness of
> modifying a header used globally (and that triggers an almost full tree
> rebuild every time it is touched) with information that is of interest only
> to code that includes the rfkill.h header.
> 
> Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>

Besides the spelling comments from Thomas, patch is fine with me. 

Acked-by: Ivo van Doorn <IvDoorn@gmail.com>

> Cc: Ivo van Doorn <IvDoorn@gmail.com>
> ---
>  include/linux/rfkill.h |    7 +++++
>  net/rfkill/rfkill.c    |   70 +++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 74 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/rfkill.h b/include/linux/rfkill.h
> index c0cab7d..98667be 100644
> --- a/include/linux/rfkill.h
> +++ b/include/linux/rfkill.h
> @@ -117,4 +117,11 @@ static inline char *rfkill_get_led_name(struct rfkill *rfkill)
>  #endif
>  }
>  
> +/* rfkill notification chain */
> +#define RFKILL_STATE_CHANGED		0x0001	/* state of a normal rfkill
> +						   switch has changed */
> +
> +int register_rfkill_notifier(struct notifier_block *nb);
> +int unregister_rfkill_notifier(struct notifier_block *nb);
> +
>  #endif /* RFKILL_H */
> diff --git a/net/rfkill/rfkill.c b/net/rfkill/rfkill.c
> index f11220b..251defe 100644
> --- a/net/rfkill/rfkill.c
> +++ b/net/rfkill/rfkill.c
> @@ -46,6 +46,49 @@ MODULE_PARM_DESC(default_state,
>  
>  static enum rfkill_state rfkill_states[RFKILL_TYPE_MAX];
>  
> +static BLOCKING_NOTIFIER_HEAD(rfkill_notifier_list);
> +
> +
> +/**
> + * register_rfkill_notifier - Add notifier to rfkill notifier chain
> + * @nb: pointer to the new entry to add to the chain
> + *
> + * See blocking_notifier_chain_register() for return value and further
> + * observations.
> + *
> + * Adds a notifier to the rfkill notifier chain.  The chain will be
> + * called with a pointer to the relevant rfkill structure as a parameter,
> + * refer to include/linux/rfkill.h for the possible events.
> + *
> + * Notifiers added to this chain are to always return NOTIFY_DONE.  This
> + * chain is a blocking notifier chain: notifiers can sleep.
> + *
> + * Calls to this chain may have been done through a workqueue.  One must
> + * one must assume unordered assynchronous behaviour, there is no way to
> + * know if actions related to the event that generated the notification
> + * have been carried out already.
> + */
> +int register_rfkill_notifier(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&rfkill_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(register_rfkill_notifier);
> +
> +/**
> + * unregister_rfkill_notifier - remove notifier from rfkill notifier chain
> + * @nb: pointer to the entry to remove from the chain
> + *
> + * See blocking_notifier_chain_unregister() for return value and further
> + * observations.
> + *
> + * Removes a notifier from the rfkill notifier chain.
> + */
> +int unregister_rfkill_notifier(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_unregister(&rfkill_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(unregister_rfkill_notifier);
> +
>  
>  static void rfkill_led_trigger(struct rfkill *rfkill,
>  			       enum rfkill_state state)
> @@ -62,14 +105,25 @@ static void rfkill_led_trigger(struct rfkill *rfkill,
>  #endif /* CONFIG_RFKILL_LEDS */
>  }
>  
> +static void notify_rfkill_state_change(struct rfkill *rfkill)
> +{
> +	blocking_notifier_call_chain(&rfkill_notifier_list,
> +			RFKILL_STATE_CHANGED,
> +			rfkill);
> +}
> +
>  static void update_rfkill_state(struct rfkill *rfkill)
>  {
> -	enum rfkill_state newstate;
> +	enum rfkill_state newstate, oldstate;
>  
>  	if (rfkill->get_state) {
>  		mutex_lock(&rfkill->mutex);
> -		if (!rfkill->get_state(rfkill->data, &newstate))
> +		if (!rfkill->get_state(rfkill->data, &newstate)) {
> +			oldstate = rfkill->state;
>  			rfkill->state = newstate;
> +			if (oldstate != newstate)
> +				notify_rfkill_state_change(rfkill);
> +		}
>  		mutex_unlock(&rfkill->mutex);
>  	}
>  }
> @@ -93,8 +147,10 @@ static int rfkill_toggle_radio(struct rfkill *rfkill,
>  			rfkill->state = state;
>  	}
>  
> -	if (force || rfkill->state != oldstate)
> +	if (force || rfkill->state != oldstate) {
>  		rfkill_led_trigger(rfkill, rfkill->state);
> +		notify_rfkill_state_change(rfkill);
> +	}
>  
>  	return retval;
>  }
> @@ -139,8 +195,16 @@ EXPORT_SYMBOL(rfkill_switch_all);
>   */
>  int rfkill_force_state(struct rfkill *rfkill, enum rfkill_state state)
>  {
> +	enum rfkill_state oldstate;
> +
>  	mutex_lock(&rfkill->mutex);
> +
> +	oldstate = rfkill->state;
>  	rfkill->state = state;
> +
> +	if (state != oldstate)
> +		notify_rfkill_state_change(rfkill);
> +
>  	mutex_unlock(&rfkill->mutex);
>  
>  	return 0;