[PATCH 3/4] input: evdev: Indicate buffer overrun with SYN_DROPPED.
STALE5670d
From: Jeff Brown <hidden>
Date: 2011-03-23 01:05:08
Also in:
lkml
Subsystem:
input (keyboard, mouse, joystick, touchscreen) drivers, the rest · Maintainers:
Dmitry Torokhov, Linus Torvalds
From: Jeff Brown <redacted> Add a new EV_SYN code, SYN_DROPPED, to inform the client when input events have been dropped from the evdev input buffer due to a buffer overrun. The client should use this event as a hint to reset its state or ignore all following events until the next packet begins. Signed-off-by: jeffbrown@android.com --- drivers/input/evdev.c | 18 ++++++++++++------ include/linux/input.h | 1 + 2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 7f42d3a..203ed70 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c@@ -57,14 +57,20 @@ static void evdev_pass_event(struct evdev_client *client, { /* * Interrupts are disabled, just acquire the lock. - * Make sure we don't leave with the client buffer - * "empty" by having client->head == client->tail. + * When the client buffer is full, replace the tail with SYN_DROPPED + * to let the client know that events were dropped. Ensure that the + * head and tail never coincide so the buffer does not appear "empty". */ spin_lock(&client->buffer_lock); - do { - client->buffer[client->head++] = *event; - client->head &= client->bufsize - 1; - } while (client->head == client->tail); + client->buffer[client->head++] = *event; + client->head &= client->bufsize - 1; + if (client->head == client->tail) { + client->tail = (client->tail + 1) & (client->bufsize - 1); + client->buffer[client->tail].time = event->time; + client->buffer[client->tail].type = EV_SYN; + client->buffer[client->tail].code = SYN_DROPPED; + client->buffer[client->tail].value = 0; + } spin_unlock(&client->buffer_lock); if (event->type == EV_SYN)
diff --git a/include/linux/input.h b/include/linux/input.h
index 056ae8a..65d253e 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h@@ -167,6 +167,7 @@ struct input_keymap_entry { #define SYN_REPORT 0 #define SYN_CONFIG 1 #define SYN_MT_REPORT 2 +#define SYN_DROPPED 3 /* * Keys and buttons
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1.7.0.4