Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934392AbcCPRAJ (ORCPT ); Wed, 16 Mar 2016 13:00:09 -0400 Received: from mail-wm0-f52.google.com ([74.125.82.52]:37816 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373AbcCPRAH (ORCPT ); Wed, 16 Mar 2016 13:00:07 -0400 From: Cyan Ogilvie To: David Herrmann , Jiri Kosina , Benjamin Tissoires Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Cyan Ogilvie Subject: [PATCH] HID: wiimote: Fix wiimote mp scale linearization Date: Wed, 16 Mar 2016 18:59:41 +0200 Message-Id: <1458147581-4126-1-git-send-email-cyan.ogilvie@gmail.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2151 Lines: 56 The wiimote motion plus gyros use two scales to report fast and slow rotation - below 440 deg/s uses 8192/440 units / deg/s, and above uses 8192/2000 units / deg/s. Previously this driver attempted to linearize the two by scaling the fast rate by 18 and the slow by 9, but this results in a scale of 8192*9/440 = ~167.564 for slow and 8192*18/2000 = 73.728 for fast. Correct the fast motion scale factor so that both report ~167.564 units / deg/s Signed-off-by: Cyan Ogilvie --- drivers/hid/hid-wiimote-modules.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/hid/hid-wiimote-modules.c b/drivers/hid/hid-wiimote-modules.c index 4390eee..c830ed3 100644 --- a/drivers/hid/hid-wiimote-modules.c +++ b/drivers/hid/hid-wiimote-modules.c @@ -2049,9 +2049,11 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext) * -----+------------------------------+-----+-----+ * The single bits Yaw, Roll, Pitch in the lower right corner specify * whether the wiimote is rotating fast (0) or slow (1). Speed for slow - * roation is 440 deg/s and for fast rotation 2000 deg/s. To get a - * linear scale we multiply by 2000/440 = ~4.5454 which is 18 for fast - * and 9 for slow. + * roation is 8192/440 units / deg/s and for fast rotation 8192/2000 + * units / deg/s. To get a linear scale for fast rotation we multiply + * by 2000/440 = ~4.5454 and scale both fast and slow by 9 to match the + * previous scale reported by this driver. + * This leaves a linear scale with 8192*9/440 (~167.564) units / deg/s. * If the wiimote is not rotating the sensor reports 2^13 = 8192. * Ext specifies whether an extension is connected to the motionp. * which is parsed by wiimote-core. @@ -2070,15 +2072,15 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext) z -= 8192; if (!(ext[3] & 0x02)) - x *= 18; + x = (x * 2000 * 9) / 440; else x *= 9; if (!(ext[4] & 0x02)) - y *= 18; + y = (y * 2000 * 9) / 440; else y *= 9; if (!(ext[3] & 0x01)) - z *= 18; + z = (z * 2000 * 9) / 440; else z *= 9; -- 2.1.4