Re: [PATCH] Input: add support for polling to input devices

[Benjamin Tissoires]

On Mon, Aug 12, 2019 at 7:11 PM Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> wrote:
>
> Hi Benjamin,
>
> On Mon, Aug 12, 2019 at 06:50:38PM +0200, Benjamin Tissoires wrote:
> > Hi Dmitry,
> >
> > On Fri, Aug 9, 2019 at 7:35 PM Dmitry Torokhov
> > <dmitry.torokhov@xxxxxxxxx> wrote:
> > >
> > > Separating "normal" and "polled" input devices was a mistake, as often we
> > > want to allow the very same device work on both interrupt-driven and
> > > polled mode, depending on the board on which the device is used.
> > >
> > > This introduces new APIs:
> > >
> > > - input_setup_polling
> > > - input_set_poll_interval
> > > - input_set_min_poll_interval
> > > - input_set_max_poll_interval
> > >
> > > These new APIs allow switching an input device into polled mode with sysfs
> > > attributes matching drivers using input_polled_dev APIs that will be
> > > eventually removed.
> >
> > Are you sure that using sysfs is the correct way here?
> > I would think using generic properties that can be overwritten by the
> > DSDT or by the device tree would make things easier from a driver
> > point of view.
>
> Couple of points: I wanted it to be compatible with input-polldev.c so
> the sysfs attributes must match (so that we can convert existing drivers
> and zap input-polldev).

Oh, I missed that. Good point.

> I also am not sure if polling parameters are
> property of board, or it is either fundamental hardware limitation or
> simply desired system behavior.

I think it's a combination of everything: sometimes the board misses
the capability to not do IRQs for that device, and using properties
would be better here: you can define them where you need (board,
platform or device level), and have a working platfrom from the kernel
description entirely.
However, it doesn't solve the issue of input-polldev, so maybe
properties should be added on top of this sysfs.

> If Rob is OK with adding device
> properties I'd be fine adding them as a followup, otherwise we can have
> udev adjust the behavior as needed for given box shortly after boot.

Fair enough.

>
> >
> > Also, checkpatch complains about a few octal permissions that are
> > preferred over symbolic ones, and there is a possible 'out of memory'
> > nessage at drivers/input/input-poller.c:75.
>
> Yes, there is. It is there so we would know what device we were trying
> to set up when OOM happened. You can probable decipher the driver from
> the stack trace, but figuring particular device instance is harder.

Could you add a comment there explaining this choice? I have a feeling
you'll have to refuse a few patches of people running coccinelle
scripts and be too happy to send a kernel patch.

Other than that:
Acked-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>

Cheers,
Benjamin

>
> Thanks.
>
> >
> > Cheers,
> > Benjamin
> >
> > >
> > > Tested-by: Michal VokÃÄ <michal.vokac@xxxxxxxxx>
> > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > > ---
> > >  drivers/input/Makefile       |   2 +-
> > >  drivers/input/input-poller.c | 208 +++++++++++++++++++++++++++++++++++
> > >  drivers/input/input-poller.h |  18 +++
> > >  drivers/input/input.c        |  36 ++++--
> > >  include/linux/input.h        |  12 ++
> > >  5 files changed, 268 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/input/Makefile b/drivers/input/Makefile
> > > index 40de6a7be641..e35650930371 100644
> > > --- a/drivers/input/Makefile
> > > +++ b/drivers/input/Makefile
> > > @@ -6,7 +6,7 @@
> > >  # Each configuration option enables a list of files.
> > >
> > >  obj-$(CONFIG_INPUT)            += input-core.o
> > > -input-core-y := input.o input-compat.o input-mt.o ff-core.o
> > > +input-core-y := input.o input-compat.o input-mt.o input-poller.o ff-core.o
> > >
> > >  obj-$(CONFIG_INPUT_FF_MEMLESS) += ff-memless.o
> > >  obj-$(CONFIG_INPUT_POLLDEV)    += input-polldev.o
> > > diff --git a/drivers/input/input-poller.c b/drivers/input/input-poller.c
> > > new file mode 100644
> > > index 000000000000..e041adb04f5a
> > > --- /dev/null
> > > +++ b/drivers/input/input-poller.c
> > > @@ -0,0 +1,208 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Support for polling mode for input devices.
> > > + */
> > > +
> > > +#include <linux/device.h>
> > > +#include <linux/input.h>
> > > +#include <linux/jiffies.h>
> > > +#include <linux/mutex.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/types.h>
> > > +#include <linux/workqueue.h>
> > > +#include "input-poller.h"
> > > +
> > > +struct input_dev_poller {
> > > +       void (*poll)(struct input_dev *dev);
> > > +
> > > +       unsigned int poll_interval; /* msec */
> > > +       unsigned int poll_interval_max; /* msec */
> > > +       unsigned int poll_interval_min; /* msec */
> > > +
> > > +       struct input_dev *input;
> > > +       struct delayed_work work;
> > > +};
> > > +
> > > +static void input_dev_poller_queue_work(struct input_dev_poller *poller)
> > > +{
> > > +       unsigned long delay;
> > > +
> > > +       delay = msecs_to_jiffies(poller->poll_interval);
> > > +       if (delay >= HZ)
> > > +               delay = round_jiffies_relative(delay);
> > > +
> > > +       queue_delayed_work(system_freezable_wq, &poller->work, delay);
> > > +}
> > > +
> > > +static void input_dev_poller_work(struct work_struct *work)
> > > +{
> > > +       struct input_dev_poller *poller =
> > > +               container_of(work, struct input_dev_poller, work.work);
> > > +
> > > +       poller->poll(poller->input);
> > > +       input_dev_poller_queue_work(poller);
> > > +}
> > > +
> > > +void input_dev_poller_finalize(struct input_dev_poller *poller)
> > > +{
> > > +       if (!poller->poll_interval)
> > > +               poller->poll_interval = 500;
> > > +       if (!poller->poll_interval_max)
> > > +               poller->poll_interval_max = poller->poll_interval;
> > > +}
> > > +
> > > +void input_dev_poller_start(struct input_dev_poller *poller)
> > > +{
> > > +       /* Only start polling if polling is enabled */
> > > +       if (poller->poll_interval > 0) {
> > > +               poller->poll(poller->input);
> > > +               input_dev_poller_queue_work(poller);
> > > +       }
> > > +}
> > > +
> > > +void input_dev_poller_stop(struct input_dev_poller *poller)
> > > +{
> > > +       cancel_delayed_work_sync(&poller->work);
> > > +}
> > > +
> > > +int input_setup_polling(struct input_dev *dev,
> > > +                       void (*poll_fn)(struct input_dev *dev))
> > > +{
> > > +       struct input_dev_poller *poller;
> > > +
> > > +       poller = kzalloc(sizeof(*poller), GFP_KERNEL);
> > > +       if (!poller) {
> > > +               dev_err(dev->dev.parent ?: &dev->dev,
> > > +                       "%s: unable to allocate poller structure\n", __func__);
> > > +               return -ENOMEM;
> > > +       }
> > > +
> > > +       INIT_DELAYED_WORK(&poller->work, input_dev_poller_work);
> > > +       poller->input = dev;
> > > +       poller->poll = poll_fn;
> > > +
> > > +       dev->poller = poller;
> > > +       return 0;
> > > +}
> > > +EXPORT_SYMBOL(input_setup_polling);
> > > +
> > > +static bool input_dev_ensure_poller(struct input_dev *dev)
> > > +{
> > > +       if (!dev->poller) {
> > > +               dev_err(dev->dev.parent ?: &dev->dev,
> > > +                       "poller structure has not been set up\n");
> > > +               return false;
> > > +       }
> > > +
> > > +       return true;
> > > +}
> > > +
> > > +void input_set_poll_interval(struct input_dev *dev, unsigned int interval)
> > > +{
> > > +       if (input_dev_ensure_poller(dev))
> > > +               dev->poller->poll_interval = interval;
> > > +}
> > > +EXPORT_SYMBOL(input_set_poll_interval);
> > > +
> > > +void input_set_min_poll_interval(struct input_dev *dev, unsigned int interval)
> > > +{
> > > +       if (input_dev_ensure_poller(dev))
> > > +               dev->poller->poll_interval_min = interval;
> > > +}
> > > +EXPORT_SYMBOL(input_set_min_poll_interval);
> > > +
> > > +void input_set_max_poll_interval(struct input_dev *dev, unsigned int interval)
> > > +{
> > > +       if (input_dev_ensure_poller(dev))
> > > +               dev->poller->poll_interval_max = interval;
> > > +}
> > > +EXPORT_SYMBOL(input_set_max_poll_interval);
> > > +
> > > +/* SYSFS interface */
> > > +
> > > +static ssize_t input_dev_get_poll_interval(struct device *dev,
> > > +                                          struct device_attribute *attr,
> > > +                                          char *buf)
> > > +{
> > > +       struct input_dev *input = to_input_dev(dev);
> > > +
> > > +       return sprintf(buf, "%d\n", input->poller->poll_interval);
> > > +}
> > > +
> > > +static ssize_t input_dev_set_poll_interval(struct device *dev,
> > > +                                          struct device_attribute *attr,
> > > +                                          const char *buf, size_t count)
> > > +{
> > > +       struct input_dev *input = to_input_dev(dev);
> > > +       struct input_dev_poller *poller = input->poller;
> > > +       unsigned int interval;
> > > +       int err;
> > > +
> > > +       err = kstrtouint(buf, 0, &interval);
> > > +       if (err)
> > > +               return err;
> > > +
> > > +       if (interval < poller->poll_interval_min)
> > > +               return -EINVAL;
> > > +
> > > +       if (interval > poller->poll_interval_max)
> > > +               return -EINVAL;
> > > +
> > > +       mutex_lock(&input->mutex);
> > > +
> > > +       poller->poll_interval = interval;
> > > +
> > > +       if (input->users) {
> > > +               cancel_delayed_work_sync(&poller->work);
> > > +               if (poller->poll_interval > 0)
> > > +                       input_dev_poller_queue_work(poller);
> > > +       }
> > > +
> > > +       mutex_unlock(&input->mutex);
> > > +
> > > +       return count;
> > > +}
> > > +
> > > +static DEVICE_ATTR(poll, S_IRUGO | S_IWUSR,
> > > +                  input_dev_get_poll_interval, input_dev_set_poll_interval);
> > > +
> > > +static ssize_t input_dev_get_poll_max(struct device *dev,
> > > +                                     struct device_attribute *attr, char *buf)
> > > +{
> > > +       struct input_dev *input = to_input_dev(dev);
> > > +
> > > +       return sprintf(buf, "%d\n", input->poller->poll_interval_max);
> > > +}
> > > +
> > > +static DEVICE_ATTR(max, S_IRUGO, input_dev_get_poll_max, NULL);
> > > +
> > > +static ssize_t input_dev_get_poll_min(struct device *dev,
> > > +                                    struct device_attribute *attr, char *buf)
> > > +{
> > > +       struct input_dev *input = to_input_dev(dev);
> > > +
> > > +       return sprintf(buf, "%d\n", input->poller->poll_interval_min);
> > > +}
> > > +
> > > +static DEVICE_ATTR(min, S_IRUGO, input_dev_get_poll_min, NULL);
> > > +
> > > +static umode_t input_poller_attrs_visible(struct kobject *kobj,
> > > +                                         struct attribute *attr, int n)
> > > +{
> > > +       struct device *dev = kobj_to_dev(kobj);
> > > +       struct input_dev *input = to_input_dev(dev);
> > > +
> > > +       return input->poller ? attr->mode : 0;
> > > +}
> > > +
> > > +static struct attribute *input_poller_attrs[] = {
> > > +       &dev_attr_poll.attr,
> > > +       &dev_attr_max.attr,
> > > +       &dev_attr_min.attr,
> > > +       NULL
> > > +};
> > > +
> > > +struct attribute_group input_poller_attribute_group = {
> > > +       .is_visible     = input_poller_attrs_visible,
> > > +       .attrs          = input_poller_attrs,
> > > +};
> > > diff --git a/drivers/input/input-poller.h b/drivers/input/input-poller.h
> > > new file mode 100644
> > > index 000000000000..e3fca0be1d32
> > > --- /dev/null
> > > +++ b/drivers/input/input-poller.h
> > > @@ -0,0 +1,18 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > > +#ifndef _INPUT_POLLER_H
> > > +#define _INPUT_POLLER_H
> > > +
> > > +/*
> > > + * Support for polling mode for input devices.
> > > + */
> > > +#include <linux/sysfs.h>
> > > +
> > > +struct input_dev_poller;
> > > +
> > > +void input_dev_poller_finalize(struct input_dev_poller *poller);
> > > +void input_dev_poller_start(struct input_dev_poller *poller);
> > > +void input_dev_poller_stop(struct input_dev_poller *poller);
> > > +
> > > +extern struct attribute_group input_poller_attribute_group;
> > > +
> > > +#endif /* _INPUT_POLLER_H */
> > > diff --git a/drivers/input/input.c b/drivers/input/input.c
> > > index 7494a0dede79..c08aa3596144 100644
> > > --- a/drivers/input/input.c
> > > +++ b/drivers/input/input.c
> > > @@ -24,6 +24,7 @@
> > >  #include <linux/mutex.h>
> > >  #include <linux/rcupdate.h>
> > >  #include "input-compat.h"
> > > +#include "input-poller.h"
> > >
> > >  MODULE_AUTHOR("Vojtech Pavlik <vojtech@xxxxxxx>");
> > >  MODULE_DESCRIPTION("Input core");
> > > @@ -603,20 +604,31 @@ int input_open_device(struct input_handle *handle)
> > >
> > >         handle->open++;
> > >
> > > -       if (!dev->users++ && dev->open)
> > > -               retval = dev->open(dev);
> > > +       if (dev->users++) {
> > > +               /*
> > > +                * Device is already opened, so we can exit immediately and
> > > +                * report success.
> > > +                */
> > > +               goto out;
> > > +       }
> > >
> > > -       if (retval) {
> > > -               dev->users--;
> > > -               if (!--handle->open) {
> > > +       if (dev->open) {
> > > +               retval = dev->open(dev);
> > > +               if (retval) {
> > > +                       dev->users--;
> > > +                       handle->open--;
> > >                         /*
> > >                          * Make sure we are not delivering any more events
> > >                          * through this handle
> > >                          */
> > >                         synchronize_rcu();
> > > +                       goto out;
> > >                 }
> > >         }
> > >
> > > +       if (dev->poller)
> > > +               input_dev_poller_start(dev->poller);
> > > +
> > >   out:
> > >         mutex_unlock(&dev->mutex);
> > >         return retval;
> > > @@ -655,8 +667,13 @@ void input_close_device(struct input_handle *handle)
> > >
> > >         __input_release_device(handle);
> > >
> > > -       if (!--dev->users && dev->close)
> > > -               dev->close(dev);
> > > +       if (!--dev->users) {
> > > +               if (dev->poller)
> > > +                       input_dev_poller_stop(dev->poller);
> > > +
> > > +               if (dev->close)
> > > +                       dev->close(dev);
> > > +       }
> > >
> > >         if (!--handle->open) {
> > >                 /*
> > > @@ -1502,6 +1519,7 @@ static const struct attribute_group *input_dev_attr_groups[] = {
> > >         &input_dev_attr_group,
> > >         &input_dev_id_attr_group,
> > >         &input_dev_caps_attr_group,
> > > +       &input_poller_attribute_group,
> > >         NULL
> > >  };
> > >
> > > @@ -1511,6 +1529,7 @@ static void input_dev_release(struct device *device)
> > >
> > >         input_ff_destroy(dev);
> > >         input_mt_destroy_slots(dev);
> > > +       kfree(dev->poller);
> > >         kfree(dev->absinfo);
> > >         kfree(dev->vals);
> > >         kfree(dev);
> > > @@ -2175,6 +2194,9 @@ int input_register_device(struct input_dev *dev)
> > >         if (!dev->setkeycode)
> > >                 dev->setkeycode = input_default_setkeycode;
> > >
> > > +       if (dev->poller)
> > > +               input_dev_poller_finalize(dev->poller);
> > > +
> > >         error = device_add(&dev->dev);
> > >         if (error)
> > >                 goto err_free_vals;
> > > diff --git a/include/linux/input.h b/include/linux/input.h
> > > index e95a439d8bd5..94f277cd806a 100644
> > > --- a/include/linux/input.h
> > > +++ b/include/linux/input.h
> > > @@ -21,6 +21,8 @@
> > >  #include <linux/timer.h>
> > >  #include <linux/mod_devicetable.h>
> > >
> > > +struct input_dev_poller;
> > > +
> > >  /**
> > >   * struct input_value - input value representation
> > >   * @type: type of value (EV_KEY, EV_ABS, etc)
> > > @@ -71,6 +73,8 @@ enum input_clock_type {
> > >   *     not sleep
> > >   * @ff: force feedback structure associated with the device if device
> > >   *     supports force feedback effects
> > > + * @poller: poller structure associated with the device if device is
> > > + *     set up to use polling mode
> > >   * @repeat_key: stores key code of the last key pressed; used to implement
> > >   *     software autorepeat
> > >   * @timer: timer for software autorepeat
> > > @@ -156,6 +160,8 @@ struct input_dev {
> > >
> > >         struct ff_device *ff;
> > >
> > > +       struct input_dev_poller *poller;
> > > +
> > >         unsigned int repeat_key;
> > >         struct timer_list timer;
> > >
> > > @@ -372,6 +378,12 @@ void input_unregister_device(struct input_dev *);
> > >
> > >  void input_reset_device(struct input_dev *);
> > >
> > > +int input_setup_polling(struct input_dev *dev,
> > > +                       void (*poll_fn)(struct input_dev *dev));
> > > +void input_set_poll_interval(struct input_dev *dev, unsigned int interval);
> > > +void input_set_min_poll_interval(struct input_dev *dev, unsigned int interval);
> > > +void input_set_max_poll_interval(struct input_dev *dev, unsigned int interval);
> > > +
> > >  int __must_check input_register_handler(struct input_handler *);
> > >  void input_unregister_handler(struct input_handler *);
> > >
> > > --
> > > 2.23.0.rc1.153.gdeed80330f-goog
> > >
> > >
> > > --
> > > Dmitry
>
> --
> Dmitry