Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758131Ab2J3KHq (ORCPT ); Tue, 30 Oct 2012 06:07:46 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:51749 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753636Ab2J3KHo (ORCPT ); Tue, 30 Oct 2012 06:07:44 -0400 MIME-Version: 1.0 In-Reply-To: <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> <20121029190554.GA15015@polaris.bitmath.org> Date: Tue, 30 Oct 2012 11:07:42 +0100 Message-ID: Subject: Re: [PATCH v2 02/11] HID: core: fix unit exponent parsing From: Benjamin Tissoires To: Henrik Rydberg Cc: Dmitry Torokhov , Jiri Kosina , Stephane Chatty , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4394 Lines: 117 Hi Henrik, On Mon, Oct 29, 2012 at 8:05 PM, Henrik Rydberg wrote: > 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? yes, but for 4-bits values. The thing is that I didn't managed to figure out if it was allowed to give unit exponent with more than 4 bits... > >> 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). but to be sure, we should still do a test against (raw_value & 0xf0) for values with more than 4 bits, no? Cheers, Benjamin > >> 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/