From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753292AbaD0IWO (ORCPT ); Sun, 27 Apr 2014 04:22:14 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38206 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753082AbaD0IWL (ORCPT ); Sun, 27 Apr 2014 04:22:11 -0400 Message-ID: <1398586927.5442.6.camel@linux-fkkt.site> Subject: Re: [PATCH v2 09/24] input: Port hid-dr to ff-memless-next From: Oliver Neukum To: Michal =?ISO-8859-1?Q?Mal=FD?= Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, dmitry.torokhov@gmail.com, jkosina@suse.cz, elias.vds@gmail.com, anssi.hannula@iki.fi, simon@mungewell.org Date: Sun, 27 Apr 2014 10:22:07 +0200 In-Reply-To: <2156054.MZkXeC543k@sigyn> References: <1398175209-9565-1-git-send-email-madcatxster@devoid-pointer.net> <1398175209-9565-10-git-send-email-madcatxster@devoid-pointer.net> <1398260463.32091.5.camel@linux-fkkt.site> <2156054.MZkXeC543k@sigyn> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.2 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2014-04-24 at 12:32 +0200, Michal Malý wrote: > On Wednesday 23 of April 2014 15:41:03 Oliver Neukum wrote: > > On Tue, 2014-04-22 at 15:59 +0200, Michal Malý wrote: > > > static int drff_play(struct input_dev *dev, void *data, > > > > > > - struct ff_effect *effect) > > > + const struct mlnx_effect_command *command) > > > > > > { > > > > > > struct hid_device *hid = input_get_drvdata(dev); > > > struct drff_device *drff = data; > > > > > > + const struct mlnx_rumble_force *rumble_force = > > > &command->u.rumble_force; > > > > > > int strong, weak; > > > > > > - strong = effect->u.rumble.strong_magnitude; > > > - weak = effect->u.rumble.weak_magnitude; > > > + strong = rumble_force->strong; > > > + weak = rumble_force->weak; > > > > > > dbg_hid("called with 0x%04x 0x%04x", strong, weak); > > > > > > - if (strong || weak) { > > > - strong = strong * 0xff / 0xffff; > > > - weak = weak * 0xff / 0xffff; > > > - > > > - /* While reverse engineering this device, I found that > > > when > > > - this value is set, it causes the strong rumble to > > > function > > > - at a near maximum speed, so we'll bypass it. */ > > > - if (weak == 0x0a) > > > - weak = 0x0b; > > > - > > > - drff->report->field[0]->value[0] = 0x51; > > > - drff->report->field[0]->value[1] = 0x00; > > > - drff->report->field[0]->value[2] = weak; > > > - drff->report->field[0]->value[4] = strong; > > > - hid_hw_request(hid, drff->report, HID_REQ_SET_REPORT); > > > - > > > - drff->report->field[0]->value[0] = 0xfa; > > > - drff->report->field[0]->value[1] = 0xfe; > > > - } else { > > > + switch (command->cmd) { > > > + case MLNX_START_RUMBLE: > > > + if (strong || weak) { > > > + strong = strong * 0xff / 0xffff; > > > + weak = weak * 0xff / 0xffff; > > > + > > > + /* While reverse engineering this device, I > > > found that when > > > + this value is set, it causes the strong rumble > > > to function > > > + at a near maximum speed, so we'll bypass it. > > > */ > > > + if (weak == 0x0a) > > > + weak = 0x0b; > > > + > > > + drff->report->field[0]->value[0] = 0x51; > > > + drff->report->field[0]->value[1] = 0x00; > > > + drff->report->field[0]->value[2] = weak; > > > + drff->report->field[0]->value[4] = strong; > > > > This looks like an endianness bug. > > I don't have a big endian machine to check but why would this be an endianness > issue? We're dealing with values all the time here, not addresses so I'd > expect the 'weak' and 'strong' values to be truncated if they won't fit into > byte. Division done beforehand makes sure that the values are within <0; 255> > range. As far as I can see this is quite common in the HID and Input code. Am > I missing something here? Sorry, I thought you were writing to 16bit variables. Regards Oliver