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 <benjamin.tissoi...@gmail.com>
> ---
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
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