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 <redacted>
---
Changes in v2:
- Coding style changes requested by [off-list ref].
drivers/input/joystick/spaceball.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/input/joystick/spaceball.c b/drivers/input/joystick/spaceball.c
index 429411c6c0a8..10e09c86e067 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"
@@ -74,10 +75,16 @@ static void spaceball_process_packet(struct spaceball* spaceball)
switch (spaceball->data[0]) {
case 'D': /* Ball data */
+ /*
+ * Skip first three bytes; read six axes worth of data.
+ * Axis values are signed 16-bit big-endian.
+ */
if (spaceball->idx != 15) return;
- for (i = 0; i < 6; i++)
+ 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 */--
2.34.1