MFC r322695:

Add support for generic MS Windows 7/8/10-compatible USB HID touchscreens
found in many laptops.

Reviewed by:		hps, gonzo, bcr (manpages)
Approved by:		gonzo (mentor)
Differential Revision:	https://reviews.freebsd.org/D12017

1 files changed, 74 insertions, 0 deletions

diff --git a/sys/dev/usb/usb_hid.c b/sys/dev/usb/usb_hid.c
index fe85f0c5560c..2c045dbed442 100644
--- a/sys/dev/usb/usb_hid.c
+++ b/sys/dev/usb/usb_hid.c
@@ -849,6 +849,80 @@ usbd_req_get_hid_desc(struct usb_device *udev, struct mtx *mtx,
 }
 
 /*------------------------------------------------------------------------*
+ * calculate HID item resolution. unit/mm for distances, unit/rad for angles
+ *------------------------------------------------------------------------*/
+int32_t
+hid_item_resolution(struct hid_item *hi)
+{
+	/*
+	 * hid unit scaling table according to HID Usage Table Review
+	 * Request 39 Tbl 17 http://www.usb.org/developers/hidpage/HUTRR39b.pdf
+	 */
+	static const int64_t scale[0x10][2] = {
+	    [0x00] = { 1, 1 },
+	    [0x01] = { 1, 10 },
+	    [0x02] = { 1, 100 },
+	    [0x03] = { 1, 1000 },
+	    [0x04] = { 1, 10000 },
+	    [0x05] = { 1, 100000 },
+	    [0x06] = { 1, 1000000 },
+	    [0x07] = { 1, 10000000 },
+	    [0x08] = { 100000000, 1 },
+	    [0x09] = { 10000000, 1 },
+	    [0x0A] = { 1000000, 1 },
+	    [0x0B] = { 100000, 1 },
+	    [0x0C] = { 10000, 1 },
+	    [0x0D] = { 1000, 1 },
+	    [0x0E] = { 100, 1 },
+	    [0x0F] = { 10, 1 },
+	};
+	int64_t logical_size;
+	int64_t physical_size;
+	int64_t multiplier;
+	int64_t divisor;
+	int64_t resolution;
+
+	switch (hi->unit) {
+	case HUM_CENTIMETER:
+		multiplier = 1;
+		divisor = 10;
+		break;
+	case HUM_INCH:
+		multiplier = 10;
+		divisor = 254;
+		break;
+	case HUM_RADIAN:
+		multiplier = 1;
+		divisor = 1;
+		break;
+	case HUM_DEGREE:
+		multiplier = 573;
+		divisor = 10;
+		break;
+	default:
+		return (0);
+	}
+
+	if ((hi->logical_maximum <= hi->logical_minimum) ||
+	    (hi->physical_maximum <= hi->physical_minimum) ||
+	    (hi->unit_exponent < 0) || (hi->unit_exponent >= nitems(scale)))
+		return (0);
+
+	logical_size = (int64_t)hi->logical_maximum -
+	    (int64_t)hi->logical_minimum;
+	physical_size = (int64_t)hi->physical_maximum -
+	    (int64_t)hi->physical_minimum;
+	/* Round to ceiling */
+	resolution = logical_size * multiplier * scale[hi->unit_exponent][0] /
+	    (physical_size * divisor * scale[hi->unit_exponent][1]);
+
+	if (resolution > INT32_MAX)
+		return (0);
+
+	return (resolution);
+}
+
+/*------------------------------------------------------------------------*
  *	hid_is_mouse
  *
  * This function will decide if a USB descriptor belongs to a USB mouse.