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

Hans de Goede
2020-06-05T17:41:44Z

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)
>
>