Re: [PATCH v2 02/11] HID: core: fix unit exponent parsing
From: Henrik Rydberg <hidden>
Date: 2012-10-29 19:01:20
Also in:
lkml
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 <redacted> ---
Standard two's complement, in other words?
quoted hunk ↗ jump to hunk
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).
quoted hunk ↗ jump to hunk
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;
--
1.7.11.7Thanks, Henrik