Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932926Ab2J2TBU (ORCPT ); Mon, 29 Oct 2012 15:01:20 -0400 Received: from smtprelay-b22.telenor.se ([195.54.99.213]:53459 "EHLO smtprelay-b22.telenor.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932370Ab2J2TBR (ORCPT ); Mon, 29 Oct 2012 15:01:17 -0400 X-SENDER-IP: [85.230.29.114] X-LISTENER: [smtp.bredband.net] X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhWdACXRjlBV5h1yPGdsb2JhbABEilK3JQICgQgZAQEBATg0gh4BAQQBJxMcIwULCANGFA0YChoTh3QDCQqyEA2JVBSKeoEdgSaEIGEDlB+BVIV5hTmIAQ X-IronPort-AV: E=Sophos;i="4.80,674,1344204000"; d="scan'208";a="141711586" From: "Henrik Rydberg" Date: Mon, 29 Oct 2012 20:05:54 +0100 To: Benjamin Tissoires Cc: Dmitry Torokhov , Jiri Kosina , Stephane Chatty , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 02/11] HID: core: fix unit exponent parsing Message-ID: <20121029190554.GA15015@polaris.bitmath.org> References: <1351241067-9521-1-git-send-email-benjamin.tissoires@gmail.com> <1351241067-9521-3-git-send-email-benjamin.tissoires@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1351241067-9521-3-git-send-email-benjamin.tissoires@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3222 Lines: 102 Hi Benjamin, > HID spec details special values for the HID field unit exponent. > Basically, the range [0x8..0xf] correspond to [-8..-1]. > > Signed-off-by: Benjamin Tissoires > --- Standard two's complement, in other words? > drivers/hid/hid-core.c | 10 +++++++++- > drivers/hid/hid-input.c | 19 +++++++++++++------ > 2 files changed, 22 insertions(+), 7 deletions(-) > > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c > index 9904776..6bde6e4 100644 > --- a/drivers/hid/hid-core.c > +++ b/drivers/hid/hid-core.c > @@ -315,6 +315,7 @@ static s32 item_sdata(struct hid_item *item) > > static int hid_parser_global(struct hid_parser *parser, struct hid_item *item) > { > + __u32 raw_value; > switch (item->tag) { > case HID_GLOBAL_ITEM_TAG_PUSH: > > @@ -365,7 +366,14 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item) > return 0; > > case HID_GLOBAL_ITEM_TAG_UNIT_EXPONENT: > - parser->global.unit_exponent = item_sdata(item); > + /* Units exponent negative numbers are given through a special > + * table. > + * See "6.2.2.7 Global Items" for more information. */ > + raw_value = item_udata(item); > + if ((raw_value >> 3) == 1) > + parser->global.unit_exponent = raw_value - 16; > + else > + parser->global.unit_exponent = raw_value; I beleive the function you want is snto32(value, 4). > return 0; > > case HID_GLOBAL_ITEM_TAG_UNIT: > diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c > index 1b0adc3..fc9f2b5 100644 > --- a/drivers/hid/hid-input.c > +++ b/drivers/hid/hid-input.c > @@ -215,7 +215,7 @@ __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code) > field->logical_minimum; > __s32 physical_extents = field->physical_maximum - > field->physical_minimum; > - __s32 prev; > + __s32 prev, tmp_exponent; > > /* Check if the extents are sane */ > if (logical_extents <= 0 || physical_extents <= 0) > @@ -235,17 +235,24 @@ __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code) > case ABS_MT_TOOL_Y: > case ABS_MT_TOUCH_MAJOR: > case ABS_MT_TOUCH_MINOR: > - if (field->unit == 0x11) { /* If centimeters */ > + if (field->unit & 0xffffff00) /* Not a length */ > + return 0; > + tmp_exponent = field->unit >> 4; > + if ((tmp_exponent >> 3) == 1) > + tmp_exponent -= 16; Ditto. > + switch (field->unit & 0xf) { > + case 0x1: /* If centimeters */ > /* Convert to millimeters */ > - unit_exponent += 1; > - } else if (field->unit == 0x13) { /* If inches */ > + unit_exponent += tmp_exponent; > + break; > + case 0x3: /* If inches */ > /* Convert to millimeters */ > prev = physical_extents; > physical_extents *= 254; > if (physical_extents < prev) > return 0; > - unit_exponent -= 1; > - } else { > + unit_exponent += tmp_exponent - 2; > + default: > return 0; > } > break; > -- > 1.7.11.7 > Thanks, Henrik -- 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/