Hi David,
On Wed, Apr 16, 2014 at 12:31:45AM +0200, David Herrmann 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 masking 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 masked events.
> This way, you have a two-level filter.
That is something I had in mind for a long time, great job!
>
> 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 event-types.
>
> Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
> ---
> drivers/input/evdev.c | 155 +++++++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/input.h | 8 +++
> 2 files changed, 163 insertions(+)
>
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index 398648b..86778c3 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -51,10 +51,139 @@ 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)
> +{
> + switch (type) {
> + case 0:
> + /* 0 is special (EV-bits instead of EV_SYN) like EVIOCGBIT */
> + return EV_CNT;
> + case EV_KEY:
> + return KEY_CNT;
> + case EV_REL:
> + return REL_CNT;
> + case EV_ABS:
> + return ABS_CNT;
> + case EV_MSC:
> + return MSC_CNT;
> + case EV_SW:
> + return SW_CNT;
> + case EV_LED:
> + return LED_CNT;
> + case EV_SND:
> + return SND_CNT;
> + case EV_FF:
> + return FF_CNT;
> + }
Maybe we need a static array of code->count mapping instead of a switch?
> +
> + return 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;
> + } else {
> + /* fake mask with all bits set */
> + out = (u8 __user*)codes;
> + for (i = 0; i < min; ++i) {
> + if (put_user((u8)0xff, out + i))
> + return -EFAULT;
> + }
> + }
> + }
> +
> + codes = (u8 __user*)codes + min;
> + codes_size -= min;
> +
> + if (codes_size > 0 && clear_user(codes, codes_size))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +/* requires the buffer lock to be held */
> +static bool __evdev_is_masked(struct evdev_client *client,
> + unsigned int type,
> + unsigned int code)
> +{
> + unsigned long *mask;
> + size_t cnt;
> +
> + /* EV_SYN and unknown codes are never masked */
So won't this mean that client is still woken up by "empty" packet if we
filter out everything but EV_SYN?
Thanks.
--
Dmitry
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