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>
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index f4109fd..f5004e2 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -315,6 +315,7 @@
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 @@
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 @@
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.
*/
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 1b0adc3..007a943 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -192,7 +192,6 @@
return -EINVAL;
}
-
/**
* hidinput_calc_abs_res - calculate an absolute axis resolution
* @field: the HID report field to calculate resolution for
@@ -235,17 +234,23 @@
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;