Re: [PATCH] hid: Fix Speedlink VAD Cezanne support for some devices
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From: Stefan Kriwanek <hidden>
Date: 2013-08-25 08:46:18
Some devices of the "Speedlink VAD Cezanne" model need more aggressive fixing than already done. I made sure through testing that this patch would not interfere with the proper working of a device that is bug-free. (The driver drops EV_REL events with abs(val) >= 256, which are not achievable even on the highest laser resolution hardware setting.) Hence, I believe it is safe to also apply to older kernels (that is, if your policy allows). The patch applies to any kernel from 3.1 to current 3.11-rc6. Signed-off-by: Stefan Kriwanek <redacted> ---
--- linux-source-3.5.0/drivers/hid/hid-speedlink.c
+++ linux-source-3.5.0-speedlink/drivers/hid/hid-speedlink.c@@ -3,7 +3,7 @@ * Fixes "jumpy" cursor and removes nonexistent keyboard LEDS from * the HID descriptor. * - * Copyright (c) 2011 Stefan Kriwanek <mail@stefankriwanek.de> + * Copyright (c) 2011, 2013 Stefan Kriwanek <dev@stefankriwanek.de> */ /*
@@ -48,8 +48,13 @@ static int speedlink_event(struct hid_de struct hid_usage *usage, __s32 value) { /* No other conditions due to usage_table. */ - /* Fix "jumpy" cursor (invalid events sent by device). */ - if (value == 256) + + /* This fixes the "jumpy" cursor occuring due to invalid events sent + * by the device. Some devices only send them with value==+256, others + * don't. However, catching abs(value)>=256 is restrictive enough not + * to interfere with devices that were bug-free (has been tested). + */ + if (abs(value) >= 256) return 1; /* Drop useless distance 0 events (on button clicks etc.) as well */ if (value == 0)