2 files changed, 42 insertions, 7 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 6c161e220868..7080a9d4b840 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -86,12 +86,14 @@ static int input_defuzz_abs_event(int value, int old_val, int fuzz)
 }
 
 /*
- * Pass event through all open handles. This function is called with
+ * Pass event first through all filters and then, if event has not been
+ * filtered out, through all open handles. This function is called with
  * dev->event_lock held and interrupts disabled.
  */
 static void input_pass_event(struct input_dev *dev,
                              unsigned int type, unsigned int code, int value)
 {
+        struct input_handler *handler;
         struct input_handle *handle;
 
         rcu_read_lock();
@@ -99,11 +101,25 @@ static void input_pass_event(struct input_dev *dev,
         handle = rcu_dereference(dev->grab);
         if (handle)
                 handle->handler->event(handle, type, code, value);
-        else
-                list_for_each_entry_rcu(handle, &dev->h_list, d_node)
-                        if (handle->open)
-                                handle->handler->event(handle,
-                                                        type, code, value);
+        else {
+                bool filtered = false;
+
+                list_for_each_entry_rcu(handle, &dev->h_list, d_node) {
+                        if (!handle->open)
+                                continue;
+
+                        handler = handle->handler;
+                        if (!handler->filter) {
+                                if (filtered)
+                                        break;
+
+                                handler->event(handle, type, code, value);
+
+                        } else if (handler->filter(handle, type, code, value))
+                                filtered = true;
+                }
+        }
+
         rcu_read_unlock();
 }
 
@@ -990,6 +1006,8 @@ static int input_handlers_seq_show(struct seq_file *seq, void *v)
         union input_seq_state *state = (union input_seq_state *)&seq->private;
 
         seq_printf(seq, "N: Number=%u Name=%s", state->pos, handler->name);
+        if (handler->filter)
+                seq_puts(seq, " (filter)");
         if (handler->fops)
                 seq_printf(seq, " Minor=%d", handler->minor);
         seq_putc(seq, '\n');
@@ -1803,7 +1821,16 @@ int input_register_handle(struct input_handle *handle)
         error = mutex_lock_interruptible(&dev->mutex);
         if (error)
                 return error;
-        list_add_tail_rcu(&handle->d_node, &dev->h_list);
+
+        /*
+         * Filters go to the head of the list, normal handlers
+         * to the tail.
+         */
+        if (handler->filter)
+                list_add_rcu(&handle->d_node, &dev->h_list);
+        else
+                list_add_tail_rcu(&handle->d_node, &dev->h_list);
+
         mutex_unlock(&dev->mutex);
 
         /*
diff --git a/include/linux/input.h b/include/linux/input.h
index 7be8a6537b57..6c9d3d49fa91 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -1198,6 +1198,8 @@ struct input_handle;
  * @event: event handler. This method is being called by input core with
  *      interrupts disabled and dev->event_lock spinlock held and so
  *      it may not sleep
+ * @filter: similar to @event; separates normal event handlers from
+ *      "filters".
  * @connect: called when attaching a handler to an input device
  * @disconnect: disconnects a handler from input device
  * @start: starts handler for given handle. This function is called by
@@ -1219,6 +1221,11 @@ struct input_handle;
  * same time. All of them will get their copy of input event generated by
  * the device.
  *
+ * The very same structure is used to implement input filters. Input core
+ * allows filters to run first and will not pass event to regular handlers
+ * if any of the filters indicate that the event should be filtered (by
+ * returning %true from their filter() method).
+ *
  * Note that input core serializes calls to connect() and disconnect()
  * methods.
  */
@@ -1227,6 +1234,7 @@ struct input_handler {
         void *private;
 
         void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
+        bool (*filter)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
         int (*connect)(struct input_handler *handler, struct input_dev *dev, const struct input_device_id *id);
         void (*disconnect)(struct input_handle *handle);
         void (*start)(struct input_handle *handle);