| Message ID | 20210727040625.2159196-1-ewhac@ewhac.org |
|---|---|
| State | Accepted |
| Commit | bc7ec91718c49d938849697cfad98fcd9877cc26 |
| Headers | show |
| Series | Input: spaceball - fix parsing of movement data packets | expand |
On Mon, Jul 26, 2021 at 09:06:24PM -0700, Leo L. Schwab wrote: > The spaceball.c module was not properly parsing the movement reports > coming from the device. [ ... ] Um... Ping? This issue still exists, and it's been around a really long time. I've been using this patch to successfully fly around QuakeWorld for several months now. Schwab
Hi Leo, On Mon, Jul 26, 2021 at 09:06:24PM -0700, Leo L. Schwab wrote: > 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... Thank you for the patch. > > Signed-off-by: Leo L. Schwab <ewhac@ewhac.org> > --- > drivers/input/joystick/spaceball.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/drivers/input/joystick/spaceball.c b/drivers/input/joystick/spaceball.c > index 429411c6c0a8..43bfb3d2fa8a 100644 > --- a/drivers/input/joystick/spaceball.c > +++ b/drivers/input/joystick/spaceball.c > @@ -74,10 +74,20 @@ 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++) > - input_report_abs(dev, spaceball_axes[i], > - (__s16)((data[2 * i + 3] << 8) | data[2 * i + 2])); > + data += 3; > + for (i = 0; > + i < ARRAY_SIZE(spaceball_axes); > + ++i, data += sizeof(__s16)) { > + input_report_abs( > + dev, > + spaceball_axes[i], > + (__s16)((data[0] << 8) | data[1])); > + } Could we write for (i == 0; i < ARRAY_SIZE(spaceball_axes); i++) input_report_abs(dev, spaceball_axes[i], (__s16)(get_unaligned_be16(&data[i * 2]); instead? Thanks!
On Mon, Dec 20, 2021 at 12:59:21AM -0800, Dmitry Torokhov wrote: > Could we write > > for (i == 0; i < ARRAY_SIZE(spaceball_axes); i++) > input_report_abs(dev, spaceball_axes[i], > (__s16)(get_unaligned_be16(&data[i * 2]); > > instead? > It's not as readable, but sure, I could do that. > for (i == 0; i < ARRAY_SIZE(spaceball_axes); i++) ^^ Pretty sure you didn't mean that :-). > input_report_abs(dev, spaceball_axes[i], > (__s16)(get_unaligned_be16(&data[i * 2]); ^^^^^^^ I'm new here, but it seems odd that an array index (shift plus add to the base pointer) is preferred over a direct pointer reference. > (__s16)(get_unaligned_be16(&data[i * 2]); ^^^^^^^^^^^^^^^^^^ Ooo! Didn't know about this; thank you! Schwab
diff --git a/drivers/input/joystick/spaceball.c b/drivers/input/joystick/spaceball.c index 429411c6c0a8..43bfb3d2fa8a 100644 --- a/drivers/input/joystick/spaceball.c +++ b/drivers/input/joystick/spaceball.c @@ -74,10 +74,20 @@ 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++) - input_report_abs(dev, spaceball_axes[i], - (__s16)((data[2 * i + 3] << 8) | data[2 * i + 2])); + data += 3; + for (i = 0; + i < ARRAY_SIZE(spaceball_axes); + ++i, data += sizeof(__s16)) { + input_report_abs( + dev, + spaceball_axes[i], + (__s16)((data[0] << 8) | data[1])); + } break; case 'K': /* Button data */
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> --- drivers/input/joystick/spaceball.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)