HID: length resolution should be reported units/mm

Input ABI requires reporting resolution on main axes in units per
millimeter, not units per inch, so we need to convert accordingly.

Tested-by: Nikolai Kondrashov <spbnick@gmail.com>
Acked-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 11 insertions, 8 deletions

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 76e1f64e9765..30af8760174b 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -162,8 +162,8 @@ static int hidinput_setkeycode(struct input_dev *dev,
  *
  * as seen in the HID specification v1.11 6.2.2.7 Global Items.
  *
- * Only exponent 1 length units are processed. Centimeters are converted to
- * inches. Degrees are converted to radians.
+ * Only exponent 1 length units are processed. Centimeters and inches are
+ * converted to millimeters. Degrees are converted to radians.
  */
 static __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
 {
@@ -184,13 +184,16 @@ static __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
          */
         if (code == ABS_X || code == ABS_Y || code == ABS_Z) {
                 if (field->unit == 0x11) {              /* If centimeters */
-                        /* Convert to inches */
-                        prev = logical_extents;
-                        logical_extents *= 254;
-                        if (logical_extents < prev)
+                        /* Convert to millimeters */
+                        unit_exponent += 1;
+                } else if (field->unit == 0x13) {       /* If inches */
+                        /* Convert to millimeters */
+                        prev = physical_extents;
+                        physical_extents *= 254;
+                        if (physical_extents < prev)
                                 return 0;
-                        unit_exponent += 2;
-                } else if (field->unit != 0x13) {       /* If not inches */
+                        unit_exponent -= 1;
+                } else {
                         return 0;
                 }
         } else if (code == ABS_RX || code == ABS_RY || code == ABS_RZ) {