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Input: spaceball - fix parsing of movement data packets

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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>
This commit is contained in:
Leo L. Schwab 2021-12-30 21:05:00 -08:00 committed by Dmitry Torokhov
parent 9f3ccdc3f6
commit bc7ec91718
1 changed files with 9 additions and 2 deletions
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11
drivers/input/joystick/spaceball.c
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@ -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 @@ static void spaceball_process_packet(struct spaceball* spaceball)
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 */