diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/hid/hid-input.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c index 6c03dcc5760..8e733b6eae2 100644 --- a/drivers/hid/hid-input.c +++ b/drivers/hid/hid-input.c @@ -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 @@ mapped: 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); |