Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754268Ab1CWBFI (ORCPT ); Tue, 22 Mar 2011 21:05:08 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:59781 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753202Ab1CWBET (ORCPT ); Tue, 22 Mar 2011 21:04:19 -0400 From: Jeff Brown To: linux-input@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jeff Brown , jeffbrown@android.com Subject: [PATCH 3/4] input: evdev: Indicate buffer overrun with SYN_DROPPED. Date: Tue, 22 Mar 2011 18:04:03 -0700 Message-Id: <1300842244-42723-4-git-send-email-jeffbrown@android.com> X-Mailer: git-send-email 1.7.0.4 In-Reply-To: <1300842244-42723-1-git-send-email-jeffbrown@android.com> References: <1300842244-42723-1-git-send-email-jeffbrown@android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2287 Lines: 65 From: Jeff Brown 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 -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/