Re: [PATCH v3 7/7] Input: Add "inhibited" property

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 6/5/20 7:33 PM, Andrzej Pietrasiewicz wrote:
> From: Patrik Fimml <patrikf@chromium.org>
> 
> Userspace might want to implement a policy to temporarily disregard input
> from certain devices, including not treating them as wakeup sources.
> 
> An example use case is a laptop, whose keyboard can be folded under the
> screen to create tablet-like experience. The user then must hold the laptop
> in such a way that it is difficult to avoid pressing the keyboard keys. It
> is therefore desirable to temporarily disregard input from the keyboard,
> until it is folded back. This obviously is a policy which should be kept
> out of the kernel, but the kernel must provide suitable means to implement
> such a policy.
> 
> This patch adds a sysfs interface for exactly this purpose.
> 
> To implement the said interface it adds an "inhibited" property to struct
> input_dev, and effectively creates four states a device can be in: closed
> uninhibited, closed inhibited, open uninhibited, open inhibited. It also
> defers calling driver's ->open() and ->close() to until they are actually
> needed, e.g. it makes no sense to prepare the underlying device for
> generating events (->open()) if the device is inhibited.
> 
>                uninhibit
> closed      <------------ closed
> uninhibited ------------> inhibited
>        | ^     inhibit        | ^
>   1st  | |               1st  | |
>   open | |               open | |
>        | |                    | |
>        | | last               | | last
>        | | close              | | close
>        v |     uninhibit      v |
> open        <------------ open
> uninhibited ------------> inhibited
> 
> The top inhibit/uninhibit transition happens when users == 0.
> The bottom inhibit/uninhibit transition happens when users > 0.
> The left open/close transition happens when !inhibited.
> The right open/close transition happens when inhibited.
> Due to all transitions being serialized with dev->mutex, it is impossible
> to have "diagonal" transitions between closed uninhibited and open
> inhibited or between open uninhibited and closed inhibited.
> 
> No new callbacks are added to drivers, because their open() and close()
> serve exactly the purpose to tell the driver to start/stop providing
> events to the input core. Consequently, open() and close() - if provided
> - are called in both inhibit and uninhibit paths.
> 
> Signed-off-by: Patrik Fimml <patrikf@chromium.org>
> Co-developed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
>   drivers/input/input.c | 115 +++++++++++++++++++++++++++++++++++++++---
>   include/linux/input.h |  12 ++++-
>   2 files changed, 118 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/input/input.c b/drivers/input/input.c
> index 41377bfa142d..4110b5797219 100644
> --- a/drivers/input/input.c
> +++ b/drivers/input/input.c
> @@ -284,8 +284,11 @@ static int input_get_disposition(struct input_dev *dev,
>   	case EV_KEY:
>   		if (is_event_supported(code, dev->keybit, KEY_MAX)) {
>   
> -			/* auto-repeat bypasses state updates */
> -			if (value == 2) {
> +			/*
> +			 * auto-repeat bypasses state updates but repeat
> +			 * events are ignored if the key is not pressed
> +			 */
> +			if (value == 2 && test_bit(code, dev->key)) {
>   				disposition = INPUT_PASS_TO_HANDLERS;
>   				break;
>   			}
> @@ -367,8 +370,13 @@ static int input_get_disposition(struct input_dev *dev,
>   static void input_handle_event(struct input_dev *dev,
>   			       unsigned int type, unsigned int code, int value)
>   {
> -	int disposition = input_get_disposition(dev, type, code, &value);
> +	int disposition;
> +
> +	/* filter-out events from inhibited devices */
> +	if (dev->inhibited)
> +		return;
>   
> +	disposition = input_get_disposition(dev, type, code, &value);
>   	if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)
>   		add_input_randomness(type, code, value);
>   
> @@ -612,7 +620,7 @@ int input_open_device(struct input_handle *handle)
>   
>   	handle->open++;
>   
> -	if (dev->users++) {
> +	if (dev->users++ || dev->inhibited) {
>   		/*
>   		 * Device is already opened, so we can exit immediately and
>   		 * report success.

It seems the comment which is part of the context here may need some
updating because of the inhibit changes ?

Otherwise this patch and the rest of the series looks good to me
now. Thank you very much for your work on this.

Regards,

Hans




> @@ -675,10 +683,9 @@ void input_close_device(struct input_handle *handle)
>   
>   	__input_release_device(handle);
>   
> -	if (!--dev->users) {
> +	if (!dev->inhibited && !--dev->users) {
>   		if (dev->poller)
>   			input_dev_poller_stop(dev->poller);
> -
>   		if (dev->close)
>   			dev->close(dev);
>   	}
> @@ -1416,12 +1423,49 @@ static ssize_t input_dev_show_properties(struct device *dev,
>   }
>   static DEVICE_ATTR(properties, S_IRUGO, input_dev_show_properties, NULL);
>   
> +static int input_inhibit_device(struct input_dev *dev);
> +static int input_uninhibit_device(struct input_dev *dev);
> +
> +static ssize_t inhibited_show(struct device *dev,
> +			      struct device_attribute *attr,
> +			      char *buf)
> +{
> +	struct input_dev *input_dev = to_input_dev(dev);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%d\n", input_dev->inhibited);
> +}
> +
> +static ssize_t inhibited_store(struct device *dev,
> +			       struct device_attribute *attr, const char *buf,
> +			       size_t len)
> +{
> +	struct input_dev *input_dev = to_input_dev(dev);
> +	ssize_t rv;
> +	bool inhibited;
> +
> +	if (strtobool(buf, &inhibited))
> +		return -EINVAL;
> +
> +	if (inhibited)
> +		rv = input_inhibit_device(input_dev);
> +	else
> +		rv = input_uninhibit_device(input_dev);
> +
> +	if (rv != 0)
> +		return rv;
> +
> +	return len;
> +}
> +
> +static DEVICE_ATTR_RW(inhibited);
> +
>   static struct attribute *input_dev_attrs[] = {
>   	&dev_attr_name.attr,
>   	&dev_attr_phys.attr,
>   	&dev_attr_uniq.attr,
>   	&dev_attr_modalias.attr,
>   	&dev_attr_properties.attr,
> +	&dev_attr_inhibited.attr,
>   	NULL
>   };
>   
> @@ -1703,6 +1747,63 @@ void input_reset_device(struct input_dev *dev)
>   }
>   EXPORT_SYMBOL(input_reset_device);
>   
> +static int input_inhibit_device(struct input_dev *dev)
> +{
> +	int ret = 0;
> +
> +	mutex_lock(&dev->mutex);
> +
> +	if (dev->inhibited)
> +		goto out;
> +
> +	if (dev->users) {
> +		if (dev->close)
> +			dev->close(dev);
> +		if (dev->poller)
> +			input_dev_poller_stop(dev->poller);
> +	}
> +
> +	spin_lock_irq(&dev->event_lock);
> +	input_dev_release_keys(dev);
> +	input_dev_toggle(dev, false);
> +	spin_unlock_irq(&dev->event_lock);
> +
> +	dev->inhibited = true;
> +
> +out:
> +	mutex_unlock(&dev->mutex);
> +	return ret;
> +}
> +
> +static int input_uninhibit_device(struct input_dev *dev)
> +{
> +	int ret = 0;
> +
> +	mutex_lock(&dev->mutex);
> +
> +	if (!dev->inhibited)
> +		goto out;
> +
> +	if (dev->users) {
> +		if (dev->open) {
> +			ret = dev->open(dev);
> +			if (ret)
> +				goto out;
> +		}
> +		if (dev->poller)
> +			input_dev_poller_start(dev->poller);
> +	}
> +
> +	dev->inhibited = false;
> +	spin_lock_irq(&dev->event_lock);
> +	input_dev_toggle(dev, true);
> +	spin_unlock_irq(&dev->event_lock);
> +
> +out:
> +	mutex_unlock(&dev->mutex);
> +	return ret;
> +}
> +
>   #ifdef CONFIG_PM_SLEEP
>   static int input_dev_suspend(struct device *dev)
>   {
> @@ -2131,7 +2232,7 @@ bool input_device_enabled(struct input_dev *dev)
>   {
>   	lockdep_assert_held(&dev->mutex);
>   
> -	return dev->users > 0;
> +	return !dev->inhibited && dev->users > 0;
>   }
>   EXPORT_SYMBOL_GPL(input_device_enabled);
>   
> diff --git a/include/linux/input.h b/include/linux/input.h
> index eda4587dba67..0354b298d874 100644
> --- a/include/linux/input.h
> +++ b/include/linux/input.h
> @@ -90,9 +90,11 @@ enum input_clock_type {
>    * @open: this method is called when the very first user calls
>    *	input_open_device(). The driver must prepare the device
>    *	to start generating events (start polling thread,
> - *	request an IRQ, submit URB, etc.)
> + *	request an IRQ, submit URB, etc.). The meaning of open() is
> + *	to start providing events to the input core.
>    * @close: this method is called when the very last user calls
> - *	input_close_device().
> + *	input_close_device(). The meaning of close() is to stop
> + *	providing events to the input core.
>    * @flush: purges the device. Most commonly used to get rid of force
>    *	feedback effects loaded into the device when disconnecting
>    *	from it
> @@ -127,6 +129,10 @@ enum input_clock_type {
>    *	and needs not be explicitly unregistered or freed.
>    * @timestamp: storage for a timestamp set by input_set_timestamp called
>    *  by a driver
> + * @inhibited: indicates that the input device is inhibited. If that is
> + * the case then input core ignores any events generated by the device.
> + * Device's close() is called when it is being inhibited and its open()
> + * is called when it is being uninhibited.
>    */
>   struct input_dev {
>   	const char *name;
> @@ -201,6 +207,8 @@ struct input_dev {
>   	bool devres_managed;
>   
>   	ktime_t timestamp[INPUT_CLK_MAX];
> +
> +	bool inhibited;
>   };
>   #define to_input_dev(d) container_of(d, struct input_dev, dev)
>   
>