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HID: add absolute axis resolution calculation 

Add absolute axis resolution calculation to the core HID layer, according to HID
specification v1.11 6.2.2.7 Global Items. Only exponent 1 length units for
X/Y/Z/RX/RY/RZ axis are supported for now.

Signed-off-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Nikolai Kondrashov 2010-09-15 14:51:14 +04:00 committed by Jiri Kosina
parent b6dc79929f
commit 4ea6e4ffb4
1 changed files with 80 additions and 0 deletions
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80
drivers/hid/hid-input.c
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@ -149,6 +149,83 @@ static int hidinput_setkeycode(struct input_dev *dev,
}
/**
* hidinput_calc_abs_res - calculate an absolute axis resolution
* @field: the HID report field to calculate resolution for
* @code: axis code
*
* The formula is:
* (logical_maximum - logical_minimum)
* resolution = ----------------------------------------------------------
* (physical_maximum - physical_minimum) * 10 ^ unit_exponent
*
* as seen in the HID specification v1.11 6.2.2.7 Global Items.
*
* Only exponent 1 length units are processed. Centimeters are converted to
* inches. Degrees are converted to radians.
*/
static __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
{
__s32 unit_exponent = field->unit_exponent;
__s32 logical_extents = field->logical_maximum -
field->logical_minimum;
__s32 physical_extents = field->physical_maximum -
field->physical_minimum;
__s32 prev;
/* Check if the extents are sane */
if (logical_extents <= 0 || physical_extents <= 0)
return 0;
/*
* Verify and convert units.
* See HID specification v1.11 6.2.2.7 Global Items for unit decoding
*/
if (code == ABS_X || code == ABS_Y || code == ABS_Z) {
if (field->unit == 0x11) { /* If centimeters */
/* Convert to inches */
prev = logical_extents;
logical_extents *= 254;
if (logical_extents < prev)
return 0;
unit_exponent += 2;
} else if (field->unit != 0x13) { /* If not inches */
return 0;
}
} else if (code == ABS_RX || code == ABS_RY || code == ABS_RZ) {
if (field->unit == 0x14) { /* If degrees */
/* Convert to radians */
prev = logical_extents;
logical_extents *= 573;
if (logical_extents < prev)
return 0;
unit_exponent += 1;
} else if (field->unit != 0x12) { /* If not radians */
return 0;
}
} else {
return 0;
}
/* Apply negative unit exponent */
for (; unit_exponent < 0; unit_exponent++) {
prev = logical_extents;
logical_extents *= 10;
if (logical_extents < prev)
return 0;
}
/* Apply positive unit exponent */
for (; unit_exponent > 0; unit_exponent--) {
prev = physical_extents;
physical_extents *= 10;
if (physical_extents < prev)
return 0;
}
/* Calculate resolution */
return logical_extents / physical_extents;
}
static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_field *field,
struct hid_usage *usage)
{
@ -537,6 +614,9 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
input_set_abs_params(input, usage->code, a, b, (b - a) >> 8, (b - a) >> 4);
else input_set_abs_params(input, usage->code, a, b, 0, 0);
input_abs_set_res(input, usage->code,
hidinput_calc_abs_res(field, usage->code));
/* use a larger default input buffer for MT devices */
if (usage->code == ABS_MT_POSITION_X && input->hint_events_per_packet == 0)
input_set_events_per_packet(input, 60);