linux-kernel - Re: [PATCH] Input: Add ioctl to block suspend while event queue is not empty.

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Date:	Thu, 16 Feb 2012 00:18:59 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	linux-input@...r.kernel.org, linux-pm@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Matthew Garrett <mjg@...hat.com>,
	Chase Douglas <chase.douglas@...onical.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: Add ioctl to block suspend while event queue is not empty.

Hi,

On Saturday, January 21, 2012, Arve Hjønnevåg wrote:
> Add an ioctl, EVIOCSSUSPENDBLOCK, to block suspend while the event
> queue is not empty. This allows userspace code to process input
> events while the device appears to be asleep.
> 
> Signed-off-by: Arve Hjønnevåg <arve@...roid.com>

Minor nit below.

> ---
>  drivers/input/evdev.c |   63 +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/input.h |    3 ++
>  2 files changed, 66 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index 76457d5..e212757 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -43,6 +43,7 @@ struct evdev_client {
>  	unsigned int tail;
>  	unsigned int packet_head; /* [future] position of the first element of next packet */
>  	spinlock_t buffer_lock; /* protects access to buffer, head and tail */
> +	struct wakeup_source *wakeup_source;
>  	struct fasync_struct *fasync;
>  	struct evdev *evdev;
>  	struct list_head node;
> @@ -75,10 +76,14 @@ static void evdev_pass_event(struct evdev_client *client,
>  		client->buffer[client->tail].value = 0;
>  
>  		client->packet_head = client->tail;
> +		if (client->wakeup_source)
> +			__pm_relax(client->wakeup_source);
>  	}
>  
>  	if (event->type == EV_SYN && event->code == SYN_REPORT) {
>  		client->packet_head = client->head;
> +		if (client->wakeup_source)
> +			__pm_stay_awake(client->wakeup_source);
>  		kill_fasync(&client->fasync, SIGIO, POLL_IN);
>  	}
>  
> @@ -255,6 +260,10 @@ static int evdev_release(struct inode *inode, struct file *file)
>  	mutex_unlock(&evdev->mutex);
>  
>  	evdev_detach_client(evdev, client);
> +	if (client->wakeup_source) {
> +		__pm_relax(client->wakeup_source);
> +		wakeup_source_unregister(client->wakeup_source);
> +	}
>  	kfree(client);
>  
>  	evdev_close_device(evdev);
> @@ -373,6 +382,9 @@ static int evdev_fetch_next_event(struct evdev_client *client,
>  	if (have_event) {
>  		*event = client->buffer[client->tail++];
>  		client->tail &= client->bufsize - 1;
> +		if (client->wakeup_source &&
> +		    client->packet_head == client->tail)
> +			__pm_relax(client->wakeup_source);
>  	}

Since __pm_relax(), __pm_stay_awake() and wakeup_source_unregister() all
check if the argument is not NULL, you can simply drop the
client->wakeup_source checks.

Also with the fix I've just posted:

http://marc.info/?l=linux-pm&m=132934445508717&w=4

I think it won't be necessary to call __pm_relax() before
wakeup_source_unregister() any more.

Thanks,
Rafael
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