Input: Send events one packet at a time

On heavy event loads, such as a multitouch driver, the irqsoff latency
can be as high as 250 us.  By accumulating a frame worth of data
before passing it on, the latency can be dramatically reduced.  As a
side effect, the special EV_SYN handling can be removed, since the
frame is now atomic.

This patch adds the events() handler callback and uses it if it
exists. The latency is improved by 50 us even without the callback.

Cc: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Tested-by: Ping Cheng <pingc@wacom.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

1 files changed, 21 insertions, 3 deletions

diff --git a/include/linux/input.h b/include/linux/input.h
index 9da4f5796fd6..ba4874302939 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -1169,6 +1169,18 @@ struct ff_effect {
 #include <linux/mod_devicetable.h>
 
 /**
+ * struct input_value - input value representation
+ * @type: type of value (EV_KEY, EV_ABS, etc)
+ * @code: the value code
+ * @value: the value
+ */
+struct input_value {
+        __u16 type;
+        __u16 code;
+        __s32 value;
+};
+
+/**
  * struct input_dev - represents an input device
  * @name: name of the device
  * @phys: physical path to the device in the system hierarchy
@@ -1240,7 +1252,6 @@ struct ff_effect {
  *      last user closes the device
  * @going_away: marks devices that are in a middle of unregistering and
  *      causes input_open_device*() fail with -ENODEV.
- * @sync: set to %true when there were no new events since last EV_SYN
  * @dev: driver model's view of this device
  * @h_list: list of input handles associated with the device. When
  *      accessing the list dev->mutex must be held
@@ -1305,12 +1316,14 @@ struct input_dev {
         unsigned int users;
         bool going_away;
 
-        bool sync;
-
         struct device dev;
 
         struct list_head        h_list;
         struct list_head        node;
+
+        unsigned int num_vals;
+        unsigned int max_vals;
+        struct input_value *vals;
 };
 #define to_input_dev(d) container_of(d, struct input_dev, dev)
 
@@ -1371,6 +1384,9 @@ 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
+ * @events: event sequence 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".
  * @match: called after comparing device's id with handler's id_table
@@ -1407,6 +1423,8 @@ struct input_handler {
         void *private;
 
         void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
+        void (*events)(struct input_handle *handle,
+                       const struct input_value *vals, unsigned int count);
         bool (*filter)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
         bool (*match)(struct input_handler *handler, struct input_dev *dev);
         int (*connect)(struct input_handler *handler, struct input_dev *dev, const struct input_device_id *id);