Input: MT - Include win8 support (cab7faca) · Commits · 戴 / test

Documentation/input/multi-touch-protocol.txt

+92 −26

Original line number	Diff line number	Diff line
		@@ -162,26 +162,48 @@ are divided into categories, to allow for partial implementation. The
		minimum set consists of ABS_MT_POSITION_X and ABS_MT_POSITION_Y, which
		allows for multiple contacts to be tracked. If the device supports it, the
		ABS_MT_TOUCH_MAJOR and ABS_MT_WIDTH_MAJOR may be used to provide the size
		of the contact area and approaching contact, respectively.
		of the contact area and approaching tool, respectively.

		The TOUCH and WIDTH parameters have a geometrical interpretation; imagine
		looking through a window at someone gently holding a finger against the
		glass. You will see two regions, one inner region consisting of the part
		of the finger actually touching the glass, and one outer region formed by
		the perimeter of the finger. The diameter of the inner region is the
		ABS_MT_TOUCH_MAJOR, the diameter of the outer region is
		ABS_MT_WIDTH_MAJOR. Now imagine the person pressing the finger harder
		against the glass. The inner region will increase, and in general, the
		ratio ABS_MT_TOUCH_MAJOR / ABS_MT_WIDTH_MAJOR, which is always smaller than
		unity, is related to the contact pressure. For pressure-based devices,
		the perimeter of the finger. The center of the touching region (a) is
		ABS_MT_POSITION_X/Y and the center of the approaching finger (b) is
		ABS_MT_TOOL_X/Y. The touch diameter is ABS_MT_TOUCH_MAJOR and the finger
		diameter is ABS_MT_WIDTH_MAJOR. Now imagine the person pressing the finger
		harder against the glass. The touch region will increase, and in general,
		the ratio ABS_MT_TOUCH_MAJOR / ABS_MT_WIDTH_MAJOR, which is always smaller
		than unity, is related to the contact pressure. For pressure-based devices,
		ABS_MT_PRESSURE may be used to provide the pressure on the contact area
		instead. Devices capable of contact hovering can use ABS_MT_DISTANCE to
		indicate the distance between the contact and the surface.

		In addition to the MAJOR parameters, the oval shape of the contact can be
		described by adding the MINOR parameters, such that MAJOR and MINOR are the
		major and minor axis of an ellipse. Finally, the orientation of the oval
		shape can be describe with the ORIENTATION parameter.

		Linux MT Win8
		__________ _______________________
		/ \ \| \|
		/ \ \| \|
		/ ____ \ \| \|
		/ / \ \ \| \|
		\ \ a \ \ \| a \|
		\ \____/ \ \| \|
		\ \ \| \|
		\ b \ \| b \|
		\ \ \| \|
		\ \ \| \|
		\ \ \| \|
		\ / \| \|
		\ / \| \|
		\ / \| \|
		\__________/ \|_______________________\|


		In addition to the MAJOR parameters, the oval shape of the touch and finger
		regions can be described by adding the MINOR parameters, such that MAJOR
		and MINOR are the major and minor axis of an ellipse. The orientation of
		the touch ellipse can be described with the ORIENTATION parameter, and the
		direction of the finger ellipse is given by the vector (a - b).

		For type A devices, further specification of the touch shape is possible
		via ABS_MT_BLOB_ID.
		@@ -224,7 +246,7 @@ tool. Omit if circular [4].
		The above four values can be used to derive additional information about
		the contact. The ratio ABS_MT_TOUCH_MAJOR / ABS_MT_WIDTH_MAJOR approximates
		the notion of pressure. The fingers of the hand and the palm all have
		different characteristic widths [1].
		different characteristic widths.

		ABS_MT_PRESSURE

		@@ -240,17 +262,24 @@ the contact is hovering above the surface.

		ABS_MT_ORIENTATION

		The orientation of the ellipse. The value should describe a signed quarter
		of a revolution clockwise around the touch center. The signed value range
		is arbitrary, but zero should be returned for a finger aligned along the Y
		axis of the surface, a negative value when finger is turned to the left, and
		a positive value when finger turned to the right. When completely aligned with
		the X axis, the range max should be returned. Orientation can be omitted
		if the touching object is circular, or if the information is not available
		in the kernel driver. Partial orientation support is possible if the device
		can distinguish between the two axis, but not (uniquely) any values in
		between. In such cases, the range of ABS_MT_ORIENTATION should be [0, 1]
		[4].
		The orientation of the touching ellipse. The value should describe a signed
		quarter of a revolution clockwise around the touch center. The signed value
		range is arbitrary, but zero should be returned for an ellipse aligned with
		the Y axis of the surface, a negative value when the ellipse is turned to
		the left, and a positive value when the ellipse is turned to the
		right. When completely aligned with the X axis, the range max should be
		returned.

		Touch ellipsis are symmetrical by default. For devices capable of true 360
		degree orientation, the reported orientation must exceed the range max to
		indicate more than a quarter of a revolution. For an upside-down finger,
		range max * 2 should be returned.

		Orientation can be omitted if the touch area is circular, or if the
		information is not available in the kernel driver. Partial orientation
		support is possible if the device can distinguish between the two axis, but
		not (uniquely) any values in between. In such cases, the range of
		ABS_MT_ORIENTATION should be [0, 1] [4].

		ABS_MT_POSITION_X

		@@ -260,6 +289,23 @@ ABS_MT_POSITION_Y

		The surface Y coordinate of the center of the touching ellipse.

		ABS_MT_TOOL_X

		The surface X coordinate of the center of the approaching tool. Omit if
		the device cannot distinguish between the intended touch point and the
		tool itself.

		ABS_MT_TOOL_Y

		The surface Y coordinate of the center of the approaching tool. Omit if the
		device cannot distinguish between the intended touch point and the tool
		itself.

		The four position values can be used to separate the position of the touch
		from the position of the tool. If both positions are present, the major
		tool axis points towards the touch point [1]. Otherwise, the tool axes are
		aligned with the touch axes.

		ABS_MT_TOOL_TYPE

		The type of approaching tool. A lot of kernel drivers cannot distinguish
		@@ -305,6 +351,28 @@ The range of ABS_MT_ORIENTATION should be set to [0, 1], to indicate that
		the device can distinguish between a finger along the Y axis (0) and a
		finger along the X axis (1).

		For win8 devices with both T and C coordinates, the position mapping is

		ABS_MT_POSITION_X := T_X
		ABS_MT_POSITION_Y := T_Y
		ABS_MT_TOOL_X := C_X
		ABS_MT_TOOL_X := C_Y

		Unfortunately, there is not enough information to specify both the touching
		ellipse and the tool ellipse, so one has to resort to approximations. One
		simple scheme, which is compatible with earlier usage, is:

		ABS_MT_TOUCH_MAJOR := min(X, Y)
		ABS_MT_TOUCH_MINOR := <not used>
		ABS_MT_ORIENTATION := <not used>
		ABS_MT_WIDTH_MAJOR := min(X, Y) + distance(T, C)
		ABS_MT_WIDTH_MINOR := min(X, Y)

		Rationale: We have no information about the orientation of the touching
		ellipse, so approximate it with an inscribed circle instead. The tool
		ellipse should align with the the vector (T - C), so the diameter must
		increase with distance(T, C). Finally, assume that the touch diameter is
		equal to the tool thickness, and we arrive at the formulas above.

		Finger Tracking
		---------------
		@@ -338,9 +406,7 @@ subsequent events of the same type refer to different fingers.
		For example usage of the type A protocol, see the bcm5974 driver. For
		example usage of the type B protocol, see the hid-egalax driver.

		[1] With the extension ABS_MT_APPROACH_X and ABS_MT_APPROACH_Y, the
		difference between the contact position and the approaching tool position
		could be used to derive tilt.
		[1] Also, the difference (TOOL_X - POSITION_X) can be used to model tilt.
		[2] The list can of course be extended.
		[3] The mtdev project: http://bitmath.org/code/mtdev/.
		[4] See the section on event computation.

include/linux/input.h

+5 −3

Original line number	Diff line number	Diff line
		@@ -806,18 +806,20 @@ struct input_keymap_entry {
		#define ABS_MT_WIDTH_MAJOR 0x32 /* Major axis of approaching ellipse */
		#define ABS_MT_WIDTH_MINOR 0x33 /* Minor axis (omit if circular) */
		#define ABS_MT_ORIENTATION 0x34 /* Ellipse orientation */
		#define ABS_MT_POSITION_X 0x35 /* Center X ellipse position */
		#define ABS_MT_POSITION_Y 0x36 /* Center Y ellipse position */
		#define ABS_MT_POSITION_X 0x35 /* Center X touch position */
		#define ABS_MT_POSITION_Y 0x36 /* Center Y touch position */
		#define ABS_MT_TOOL_TYPE 0x37 /* Type of touching device */
		#define ABS_MT_BLOB_ID 0x38 /* Group a set of packets as a blob */
		#define ABS_MT_TRACKING_ID 0x39 /* Unique ID of initiated contact */
		#define ABS_MT_PRESSURE 0x3a /* Pressure on contact area */
		#define ABS_MT_DISTANCE 0x3b /* Contact hover distance */
		#define ABS_MT_TOOL_X 0x3c /* Center X tool position */
		#define ABS_MT_TOOL_Y 0x3d /* Center Y tool position */

		#ifdef __KERNEL__
		/* Implementation details, userspace should not care about these */
		#define ABS_MT_FIRST ABS_MT_TOUCH_MAJOR
		#define ABS_MT_LAST ABS_MT_DISTANCE
		#define ABS_MT_LAST ABS_MT_TOOL_Y
		#endif

		#define ABS_MAX 0x3f

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