Input: spaceball - fix parsing of movement data packets
commit bc7ec91718c49d938849697cfad98fcd9877cc26 upstream.
The spaceball.c module was not properly parsing the movement reports
coming from the device. The code read axis data as signed 16-bit
little-endian values starting at offset 2.
In fact, axis data in Spaceball movement reports are signed 16-bit
big-endian values starting at offset 3. This was determined first by
visually inspecting the data packets, and later verified by consulting:
http://spacemice.org/pdf/SpaceBall_2003-3003_Protocol.pdf
If this ever worked properly, it was in the time before Git...
Signed-off-by: Leo L. Schwab <ewhac@ewhac.org>
Link: https://lore.kernel.org/r/20211221101630.1146385-1-ewhac@ewhac.org
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/input/joystick/spaceball.c b/drivers/input/joystick/spaceball.c
index 429411c..a85a4f3 100644
--- a/drivers/input/joystick/spaceball.c
+++ b/drivers/input/joystick/spaceball.c
@@ -19,6 +19,7 @@
#include <linux/module.h>
#include <linux/input.h>
#include <linux/serio.h>
+#include <asm/unaligned.h>
#define DRIVER_DESC "SpaceTec SpaceBall 2003/3003/4000 FLX driver"
@@ -75,9 +76,15 @@
case 'D': /* Ball data */
if (spaceball->idx != 15) return;
- for (i = 0; i < 6; i++)
+ /*
+ * Skip first three bytes; read six axes worth of data.
+ * Axis values are signed 16-bit big-endian.
+ */
+ data += 3;
+ for (i = 0; i < ARRAY_SIZE(spaceball_axes); i++) {
input_report_abs(dev, spaceball_axes[i],
- (__s16)((data[2 * i + 3] << 8) | data[2 * i + 2]));
+ (__s16)get_unaligned_be16(&data[i * 2]));
+ }
break;
case 'K': /* Button data */
