[PATCH 3.12 181/212] HID:hid-lg4ff: Scale autocentering force properly on Logitech wheel

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Simon Wood <simon@xxxxxxxxxxxxx>

commit f8c231569a7a455dfa1907294a46ba52b3aa8859 upstream.

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

Reported-by: Elias Vanderstuyft <elias.vds@xxxxxxxxx>
Signed-off-by: Simon Wood <simon@xxxxxxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/hid/hid-lg4ff.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -218,12 +218,21 @@ static void hid_lg4ff_set_autocenter_def
 	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;
 


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