linux-kernel - Re: [PATCH 3/4] Input: simplify event handling logic

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Date: Mon, 1 Jul 2024 09:41:22 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: linux-input@...r.kernel.org, Jeff LaBundy <jeff@...undy.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] Input: simplify event handling logic

On Jun 30 2024, Dmitry Torokhov wrote:
> Streamline event handling code by providing batch implementations for
> filtering and event processing and using them in place of the main
> event handler, as needed, instead of having complex branching logic
> in the middle of the event processing code.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/input/input.c | 90 ++++++++++++++++++++++++-------------------
>  1 file changed, 51 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/input/input.c b/drivers/input/input.c
> index 8434348faeac..eeb755cb12e7 100644
> --- a/drivers/input/input.c
> +++ b/drivers/input/input.c
> @@ -99,41 +99,6 @@ static void input_stop_autorepeat(struct input_dev *dev)
>  	del_timer(&dev->timer);
>  }
>  
> -/*
> - * Pass event first through all filters and then, if event has not been
> - * filtered out, through all open handles. This function is called with
> - * dev->event_lock held and interrupts disabled.
> - */
> -static unsigned int input_to_handler(struct input_handle *handle,
> -			struct input_value *vals, unsigned int count)
> -{
> -	struct input_handler *handler = handle->handler;
> -	struct input_value *end = vals;
> -	struct input_value *v;
> -
> -	if (handler->filter) {
> -		for (v = vals; v != vals + count; v++) {
> -			if (handler->filter(handle, v->type, v->code, v->value))
> -				continue;
> -			if (end != v)
> -				*end = *v;
> -			end++;
> -		}
> -		count = end - vals;
> -	}
> -
> -	if (!count)
> -		return 0;
> -
> -	if (handler->events)
> -		handler->events(handle, vals, count);
> -	else if (handler->event)
> -		for (v = vals; v != vals + count; v++)
> -			handler->event(handle, v->type, v->code, v->value);
> -
> -	return count;
> -}
> -
>  /*
>   * Pass values first through all filters and then, if event has not been
>   * filtered out, through all open handles. This function is called with

Nitpick: maybe that comment above input_pass_values() should also be
amended now that the processing is more straightforward?

> @@ -154,11 +119,12 @@ static void input_pass_values(struct input_dev *dev,
>  
>  	handle = rcu_dereference(dev->grab);
>  	if (handle) {
> -		count = input_to_handler(handle, vals, count);
> +		count = handle->handler->events(handle, vals, count);
>  	} else {
>  		list_for_each_entry_rcu(handle, &dev->h_list, d_node)
>  			if (handle->open) {
> -				count = input_to_handler(handle, vals, count);
> +				count = handle->handler->events(handle, vals,
> +								count);
>  				if (!count)
>  					break;
>  			}
> @@ -2537,6 +2503,47 @@ static int input_handler_check_methods(const struct input_handler *handler)
>  	return 0;
>  }
>  
> +/*
> + * An implementation of input_handler's events() method that simply
> + * invokes handler->event() method for each event one by one.
> + */
> +static unsigned int input_handler_events_default(struct input_handle *handle,
> +						 struct input_value *vals,
> +						 unsigned int count)
> +{
> +	struct input_handler *handler = handle->handler;
> +	struct input_value *v;
> +
> +	for (v = vals; v != vals + count; v++)
> +		handler->event(handle, v->type, v->code, v->value);
> +
> +	return count;
> +}
> +
> +/*
> + * An implementation of input_handler's events() method that invokes
> + * handler->filter() method for each event one by one and removes events
> + * that were filtered out from the "vals" array.
> + */
> +static unsigned int input_handler_events_filter(struct input_handle *handle,
> +						struct input_value *vals,
> +						unsigned int count)
> +{
> +	struct input_handler *handler = handle->handler;
> +	struct input_value *end = vals;
> +	struct input_value *v;
> +
> +	for (v = vals; v != vals + count; v++) {
> +		if (handler->filter(handle, v->type, v->code, v->value))
> +			continue;
> +		if (end != v)
> +			*end = *v;
> +		end++;
> +	}
> +
> +	return end - vals;
> +}
> +
>  /**
>   * input_register_handler - register a new input handler
>   * @handler: handler to be registered
> @@ -2554,12 +2561,17 @@ int input_register_handler(struct input_handler *handler)
>  	if (error)
>  		return error;
>  
> +	INIT_LIST_HEAD(&handler->h_list);
> +
> +	if (handler->filter)
> +		handler->events = input_handler_events_filter;
> +	else if (handler->event)
> +		handler->events = input_handler_events_default;
> +
>  	error = mutex_lock_interruptible(&input_mutex);
>  	if (error)
>  		return error;
>  
> -	INIT_LIST_HEAD(&handler->h_list);
> -
>  	list_add_tail(&handler->node, &input_handler_list);
>  
>  	list_for_each_entry(dev, &input_dev_list, node)
> -- 
> 2.45.2.803.g4e1b14247a-goog
> 

Minor nitpick, but otherwise:

Reviewed-by: Benjamin Tissoires <bentiss@...nel.org>

Cheers,
Benjamin