HID: wiimote: Fix IR data parser

We incorrectly parse incoming IR data. The extra byte contains the upper
bits and not the lower bits of the x/y coordinates. User-space expects
absolute position data from us so this patch does not break existing
applications. On the contrary, it extends the virtual view and fixes
garbage reports for margin areas of the virtual screen.

Cc: stable@kernel.org
Reported-by: Peter Bukovsky <bukovsky.peter@gmail.com>
Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 5 insertions, 11 deletions

diff --git a/drivers/hid/hid-wiimote-core.c b/drivers/hid/hid-wiimote-core.c
index cac3589..84e2fbe 100644
--- a/drivers/hid/hid-wiimote-core.c
+++ b/drivers/hid/hid-wiimote-core.c
@@ -769,7 +769,7 @@ static void __ir_to_input(struct wiimote_data *wdata, const __u8 *ir,
 
 	/*
 	 * Basic IR data is encoded into 3 bytes. The first two bytes are the
-	 * upper 8 bit of the X/Y data, the 3rd byte contains the lower 2 bits
+	 * lower 8 bit of the X/Y data, the 3rd byte contains the upper 2 bits
 	 * of both.
 	 * If data is packed, then the 3rd byte is put first and slightly
 	 * reordered. This allows to interleave packed and non-packed data to
@@ -778,17 +778,11 @@ static void __ir_to_input(struct wiimote_data *wdata, const __u8 *ir,
 	 */
 
 	if (packed) {
-		x = ir[1] << 2;
-		y = ir[2] << 2;
-
-		x |= ir[0] & 0x3;
-		y |= (ir[0] >> 2) & 0x3;
+		x = ir[1] | ((ir[0] & 0x03) << 8);
+		y = ir[2] | ((ir[0] & 0x0c) << 6);
 	} else {
-		x = ir[0] << 2;
-		y = ir[1] << 2;
-
-		x |= (ir[2] >> 4) & 0x3;
-		y |= (ir[2] >> 6) & 0x3;
+		x = ir[0] | ((ir[2] & 0x30) << 4);
+		y = ir[1] | ((ir[2] & 0xc0) << 2);
 	}
 
 	input_report_abs(wdata->ir, xid, x);