[RESEND,RESEND] Input: evdev - add event-mask API

Hi David,

On Sun, Sep 28, 2014 at 12:19:39PM +0200, David Herrmann wrote:
> Ping?

Sorry for the delay.

> 
> On Wed, Aug 13, 2014 at 9:16 AM, David Herrmann <dh.herrmann@gmail.com> wrote:
> > Hardware manufacturers group keys in the weirdest way possible. This may
> > cause a power-key to be grouped together with normal keyboard keys and
> > thus be reported on the same kernel interface.
> >
> > However, user-space is often only interested in specific sets of events.
> > For instance, daemons dealing with system-reboot (like systemd-logind)
> > listen for KEY_POWER, but are not interested in any main keyboard keys.
> > Usually, power keys are reported via separate interfaces, however,
> > some i8042 boards report it in the AT matrix. To avoid waking up those
> > system daemons on each key-press, we had two ideas:
> >  - split off KEY_POWER into a separate interface unconditionally
> >  - allow filtering a specific set of events on evdev FDs
> >
> > Splitting of KEY_POWER is a rather weird way to deal with this and may
> > break backwards-compatibility. It is also specific to KEY_POWER and might
> > be required for other stuff, too. Moreover, we might end up with a huge
> > set of input-devices just to have them properly split.
> >
> > Hence, this patchset implements the second idea: An event-mask to specify
> > which events you're interested in. Two ioctls allow setting this mask for
> > each event-type. If not set, all events are reported. The type==0 entry is
> > used same as in EVIOCGBIT to set the actual EV_* mask of filtered events.
> > This way, you have a two-level filter.
> >
> > We are heavily forward-compatible to new event-types and event-codes. So
> > new user-space will be able to run on an old kernel which doesn't know the
> > given event-codes or event-types.
> >
> > Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
> > Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
> > ---
> > Hi Dmitry
> >
> > We could really make use of this for SUSPEND/POWER key handling. We keep getting
> > reports from people where those keys are reported as part of the main keyboard.
> > It's really annoying if we have to wake up those processes for *every*
> > key-press.
> >
> > In case you just need time to review it, let me know. Otherwise, I will keep
> > resending it as people ask me for it all the time.
> >
> > Thanks
> > David
> >
> >  drivers/input/evdev.c      | 156 ++++++++++++++++++++++++++++++++++++++++++++-
> >  include/uapi/linux/input.h |  56 ++++++++++++++++
> >  2 files changed, 210 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> > index fd325ec..6386882 100644
> > --- a/drivers/input/evdev.c
> > +++ b/drivers/input/evdev.c
> > @@ -51,10 +51,130 @@ struct evdev_client {
> >         struct list_head node;
> >         int clkid;
> >         bool revoked;
> > +       unsigned long *evmasks[EV_CNT];
> >         unsigned int bufsize;
> >         struct input_event buffer[];
> >  };
> >
> > +static size_t evdev_get_mask_cnt(unsigned int type)
> > +{
> > +       static size_t counts[EV_CNT] = {
> > +               /* EV_SYN==0 is EV_CNT, _not_ SYN_CNT, see EVIOCGBIT */
> > +               [EV_SYN] = EV_CNT,
> > +               [EV_KEY] = KEY_CNT,
> > +               [EV_REL] = REL_CNT,
> > +               [EV_ABS] = ABS_CNT,
> > +               [EV_MSC] = MSC_CNT,
> > +               [EV_SW] = SW_CNT,
> > +               [EV_LED] = LED_CNT,
> > +               [EV_SND] = SND_CNT,
> > +               [EV_FF] = FF_CNT,
> > +       };
> > +
> > +       return (type < EV_CNT) ? counts[type] : 0;
> > +}
> > +
> > +/* must be called with evdev-mutex held */
> > +static int evdev_set_mask(struct evdev_client *client,
> > +                         unsigned int type,
> > +                         const void __user *codes,
> > +                         u32 codes_size)
> > +{
> > +       unsigned long flags, *mask, *oldmask;
> > +       size_t cnt, size;
> > +
> > +       /* unknown masks are simply ignored for forward-compat */
> > +       cnt = evdev_get_mask_cnt(type);
> > +       if (!cnt)
> > +               return 0;
> > +
> > +       /* we allow 'codes_size > size' for forward-compat */
> > +       size = sizeof(unsigned long) * BITS_TO_LONGS(cnt);
> > +
> > +       mask = kzalloc(size, GFP_KERNEL);
> > +       if (!mask)
> > +               return -ENOMEM;
> > +
> > +       if (copy_from_user(mask, codes, min_t(size_t, codes_size, size))) {
> > +               kfree(mask);
> > +               return -EFAULT;
> > +       }
> > +
> > +       spin_lock_irqsave(&client->buffer_lock, flags);
> > +       oldmask = client->evmasks[type];
> > +       client->evmasks[type] = mask;
> > +       spin_unlock_irqrestore(&client->buffer_lock, flags);
> > +
> > +       kfree(oldmask);
> > +
> > +       return 0;
> > +}
> > +
> > +/* must be called with evdev-mutex held */
> > +static int evdev_get_mask(struct evdev_client *client,
> > +                         unsigned int type,
> > +                         void __user *codes,
> > +                         u32 codes_size)
> > +{
> > +       unsigned long *mask;
> > +       size_t cnt, size, min, i;
> > +       u8 __user *out;
> > +
> > +       /* we allow unknown types and 'codes_size > size' for forward-compat */
> > +       cnt = evdev_get_mask_cnt(type);
> > +       size = sizeof(unsigned long) * BITS_TO_LONGS(cnt);
> > +       min = min_t(size_t, codes_size, size);
> > +
> > +       if (cnt > 0) {
> > +               mask = client->evmasks[type];
> > +               if (mask) {
> > +                       if (copy_to_user(codes, mask, min))
> > +                               return -EFAULT;

I do not think this will work on big-endian setups with 64 bit kernel
and 32 bits userspace. We already have bits_to_user(), we shoudl use
them here. And I guess we need bits_from_user() to fetch bits from
userspace into kernel.

I also tried changing verbage on the ioctls, see if you agree with the
changes and if so please incorporate in your next version.

Thanks.

[RESEND,RESEND] Input: evdev - add event-mask API

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