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Commit 77463838 authored by Benjamin Tissoires's avatar Benjamin Tissoires Committed by Jiri Kosina
Browse files

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: default avatarBenjamin Tissoires <benjamin.tissoires@gmail.com>
Acked-by: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent ccdd6994

drivers/hid/hid-core.c

+15 −1
Original line number Diff line number Diff line
@@ -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

		 * two's complement.

		 * See "6.2.2.7 Global Items" for more information. */

		raw_value = item_udata(item);

		if (!(raw_value & 0xfffffff0))

			parser->global.unit_exponent = hid_snto32(raw_value, 4);

		else

			parser->global.unit_exponent = raw_value;

		return 0;



	case HID_GLOBAL_ITEM_TAG_UNIT:
@@ -865,6 +873,12 @@ static s32 snto32(__u32 value, unsigned n) 
	return value & (1 << (n - 1)) ? value | (-1 << n) : value;

}



s32 hid_snto32(__u32 value, unsigned n)

{

	return snto32(value, n);

}

EXPORT_SYMBOL_GPL(hid_snto32);



/*

 * Convert a signed 32-bit integer to a signed n-bit integer.

 */

drivers/hid/hid-input.c

+9 −4
Original line number Diff line number Diff line
@@ -192,7 +192,6 @@ static int hidinput_setkeycode(struct input_dev *dev, 
	return -EINVAL;

}





/**

 * hidinput_calc_abs_res - calculate an absolute axis resolution

 * @field: the HID report field to calculate resolution for
@@ -235,17 +234,23 @@ __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;

		unit_exponent += hid_snto32(field->unit >> 4, 4) - 1;

		switch (field->unit & 0xf) {

		case 0x1:				/* If centimeters */

			/* Convert to millimeters */

			unit_exponent += 1;

		} else if (field->unit == 0x13) {	/* If inches */

			break;

		case 0x3:				/* If inches */

			/* Convert to millimeters */

			prev = physical_extents;

			physical_extents *= 254;

			if (physical_extents < prev)

				return 0;

			unit_exponent -= 1;

		} else {

			break;

		default:

			return 0;

		}

		break;

include/linux/hid.h

+1 −0
Original line number Diff line number Diff line
@@ -717,6 +717,7 @@ int hid_connect(struct hid_device *hid, unsigned int connect_mask); 
void hid_disconnect(struct hid_device *hid);

const struct hid_device_id *hid_match_id(struct hid_device *hdev,

					 const struct hid_device_id *id);

s32 hid_snto32(__u32 value, unsigned n);



/**

 * hid_map_usage - map usage input bits