HID: fix unit exponent parsing
HID spec details special values for the HID field unit exponent. Basically, the range [0x8..0xf] correspond to [-8..-1], so this is a standard two's complement on a half-byte. Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com> Acked-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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@ -315,6 +315,7 @@ static s32 item_sdata(struct hid_item *item)
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static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
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{
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__u32 raw_value;
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switch (item->tag) {
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case HID_GLOBAL_ITEM_TAG_PUSH:
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@ -365,7 +366,14 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
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return 0;
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case HID_GLOBAL_ITEM_TAG_UNIT_EXPONENT:
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parser->global.unit_exponent = item_sdata(item);
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/* Units exponent negative numbers are given through a
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* two's complement.
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* See "6.2.2.7 Global Items" for more information. */
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raw_value = item_udata(item);
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if (!(raw_value & 0xfffffff0))
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parser->global.unit_exponent = hid_snto32(raw_value, 4);
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else
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parser->global.unit_exponent = raw_value;
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return 0;
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case HID_GLOBAL_ITEM_TAG_UNIT:
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@ -865,6 +873,12 @@ static s32 snto32(__u32 value, unsigned n)
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return value & (1 << (n - 1)) ? value | (-1 << n) : value;
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}
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s32 hid_snto32(__u32 value, unsigned n)
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{
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return snto32(value, n);
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}
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EXPORT_SYMBOL_GPL(hid_snto32);
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/*
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* Convert a signed 32-bit integer to a signed n-bit integer.
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*/
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@ -192,7 +192,6 @@ static int hidinput_setkeycode(struct input_dev *dev,
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return -EINVAL;
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}
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/**
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* hidinput_calc_abs_res - calculate an absolute axis resolution
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* @field: the HID report field to calculate resolution for
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@ -235,17 +234,23 @@ __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
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case ABS_MT_TOOL_Y:
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case ABS_MT_TOUCH_MAJOR:
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case ABS_MT_TOUCH_MINOR:
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if (field->unit == 0x11) { /* If centimeters */
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if (field->unit & 0xffffff00) /* Not a length */
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return 0;
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unit_exponent += hid_snto32(field->unit >> 4, 4) - 1;
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switch (field->unit & 0xf) {
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case 0x1: /* If centimeters */
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/* Convert to millimeters */
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unit_exponent += 1;
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} else if (field->unit == 0x13) { /* If inches */
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break;
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case 0x3: /* If inches */
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/* Convert to millimeters */
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prev = physical_extents;
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physical_extents *= 254;
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if (physical_extents < prev)
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return 0;
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unit_exponent -= 1;
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} else {
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break;
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default:
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return 0;
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}
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break;
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@ -717,6 +717,7 @@ int hid_connect(struct hid_device *hid, unsigned int connect_mask);
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void hid_disconnect(struct hid_device *hid);
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const struct hid_device_id *hid_match_id(struct hid_device *hdev,
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const struct hid_device_id *id);
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s32 hid_snto32(__u32 value, unsigned n);
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/**
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* hid_map_usage - map usage input bits
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