HID:hid-lg4ff: Scale autocentering force properly on Logitech wheel

Adjust the scaling and lineartity to match that of the Windows
driver (from MOMO testing).

Reported-by: Elias Vanderstuyft <elias.vds@gmail.com>
Signed-off-by: Simon Wood <simon@mungewell.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 12 insertions, 3 deletions

diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index 8782fe1aaa07..530fcd19e90e 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -218,12 +218,21 @@ static void hid_lg4ff_set_autocenter_default(struct input_dev *dev, u16 magnitud
         struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
         struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
         __s32 *value = report->field[0]->value;
+        __u32 expand_a, expand_b;
+
+        if (magnitude <= 0xaaaa) {
+                expand_a = 0x0c * magnitude;
+                expand_b = 0x80 * magnitude;
+        } else {
+                expand_a = (0x0c * 0xaaaa) + 0x06 * (magnitude - 0xaaaa);
+                expand_b = (0x80 * 0xaaaa) + 0xff * (magnitude - 0xaaaa);
+        }
 
         value[0] = 0xfe;
         value[1] = 0x0d;
-        value[2] = magnitude >> 13;
-        value[3] = magnitude >> 13;
-        value[4] = magnitude >> 8;
+        value[2] = expand_a / 0xaaaa;
+        value[3] = expand_a / 0xaaaa;
+        value[4] = expand_b / 0xaaaa;
         value[5] = 0x00;
         value[6] = 0x00;