Patchwork [3/3] UBUNTU: (evdev) Use driver hint to compute the evdev buffer size (rev2)

login
register
mail settings
Submitter Henrik Rydberg
Date June 10, 2010, 9:52 a.m.
Message ID <1276163579-22224-4-git-send-email-rydberg@euromail.se>
Download mbox | patch
Permalink /patch/55179/
State Accepted
Delegated to: Leann Ogasawara
Headers show

Comments

Henrik Rydberg - June 10, 2010, 9:52 a.m.
Some devices, in particular MT devices, produce a lot of data.  This
leads to a high frequency of lost packets in evdev, which by default
uses a fairly small event buffer. Let the drivers hint the average
number of events per packet for the device by calling the
input_set_events_per_packet(), and use that information when computing
the evdev buffer size.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
---
 drivers/input/evdev.c |    5 ++++-
 include/linux/input.h |   17 +++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletions(-)

Patch

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 463bf1b..2cf7b3a 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -11,6 +11,7 @@ 
 #define EVDEV_MINOR_BASE	64
 #define EVDEV_MINORS		32
 #define EVDEV_MIN_BUFFER_SIZE	64
+#define EVDEV_BUF_PACKETS	8
 
 #include <linux/poll.h>
 #include <linux/sched.h>
@@ -797,7 +798,9 @@  static void evdev_cleanup(struct evdev *evdev)
 
 static int evdev_compute_buffer_size(struct input_dev *dev)
 {
-	return EVDEV_MIN_BUFFER_SIZE;
+	int nev = dev->hint_events_per_packet * EVDEV_BUF_PACKETS;
+	nev = max(nev, EVDEV_MIN_BUFFER_SIZE);
+	return roundup_pow_of_two(nev);
 }
 
 /*
diff --git a/include/linux/input.h b/include/linux/input.h
index 20e4eac..9e024b6 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -1162,6 +1162,8 @@  struct input_dev {
 	unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
 	unsigned long swbit[BITS_TO_LONGS(SW_CNT)];
 
+	unsigned int hint_events_per_packet;
+
 	unsigned int keycodemax;
 	unsigned int keycodesize;
 	void *keycode;
@@ -1439,6 +1441,21 @@  static inline void input_mt_slot(struct input_dev *dev, int slot)
 
 void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code);
 
+/**
+ * input_set_events_per_packet - tell handlers about the driver event rate
+ * @dev: the input device used by the driver
+ * @nev: the average number of events between calls to input_sync()
+ *
+ * If the event rate sent from a device is unusually large, use this
+ * function to set the expected event rate. This will allow handlers
+ * to set up an approriate buffer size for the event stream, in order
+ * to minimize information loss.
+ */
+static inline void input_set_events_per_packet(struct input_dev *dev, int nev)
+{
+	dev->hint_events_per_packet = nev;
+}
+
 static inline void input_set_abs_params(struct input_dev *dev, int axis, int min, int max, int fuzz, int flat)
 {
 	dev->absmin[axis] = min;