diff options
| -rw-r--r-- | Documentation/input/event-codes.txt | 6 | ||||
| -rw-r--r-- | drivers/input/evdev.c | 33 | ||||
| -rw-r--r-- | include/linux/input.h | 1 |
3 files changed, 28 insertions, 12 deletions
diff --git a/Documentation/input/event-codes.txt b/Documentation/input/event-codes.txt index f13aee550409..23fcb05175be 100644 --- a/Documentation/input/event-codes.txt +++ b/Documentation/input/event-codes.txt @@ -85,6 +85,12 @@ sent in the evdev event stream. - Used to synchronize and separate touch events. See the multi-touch-protocol.txt document for more information. +* SYN_DROPPED: + - Used to indicate buffer overrun in the evdev client's event queue. + Client should ignore all events up to and including next SYN_REPORT + event and query the device (using EVIOCG* ioctls) to obtain its + current state. + EV_KEY: ---------- EV_KEY events take the form KEY_<name> or BTN_<name>. For example, KEY_A is used diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c index 7f42d3a454d2..88d8e4cb419a 100644 --- a/drivers/input/evdev.c +++ b/drivers/input/evdev.c @@ -39,13 +39,13 @@ struct evdev { }; struct evdev_client { - int head; - int tail; + unsigned int head; + unsigned int tail; spinlock_t buffer_lock; /* protects access to buffer, head and tail */ struct fasync_struct *fasync; struct evdev *evdev; struct list_head node; - int bufsize; + unsigned int bufsize; struct input_event buffer[]; }; @@ -55,16 +55,25 @@ static DEFINE_MUTEX(evdev_table_mutex); static void evdev_pass_event(struct evdev_client *client, struct input_event *event) { - /* - * Interrupts are disabled, just acquire the lock. - * Make sure we don't leave with the client buffer - * "empty" by having client->head == client->tail. - */ + /* Interrupts are disabled, just acquire the lock. */ 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 (unlikely(client->head == client->tail)) { + /* + * This effectively "drops" all unconsumed events, leaving + * EV_SYN/SYN_DROPPED plus the newest event in the queue. + */ + client->tail = (client->head - 2) & (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 0cc25e4ce2ab..73a8c6ee595b 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 |
