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@xxxxxxxxxxx>
---
drivers/input/evdev.c | 5 ++++-
include/linux/input.h | 7 +++++++
2 files changed, 11 insertions(+), 1 deletions(-)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index ea652cc..03ce9c1 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>
@@ -792,7 +793,9 @@ 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 bd00786..35b015d 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 +1441,11 @@ 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);
+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;
--
1.6.3.3
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