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| author | Siarhei Vishniakou <svv@google.com> | 2025-11-11 15:45:19 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-02-11 13:37:22 +0100 |
| commit | 4040793c74c7dba01e6b4f4c4b55b0cfd0cd39b5 (patch) | |
| tree | f848933b5af43761308af23998af49f9d5a9f14c | |
| parent | 4fb5a78b35575b7c0376521d0778094ed5e8ff40 (diff) | |
| download | linux-4040793c74c7dba01e6b4f4c4b55b0cfd0cd39b5.tar.gz linux-4040793c74c7dba01e6b4f4c4b55b0cfd0cd39b5.tar.bz2 linux-4040793c74c7dba01e6b4f4c4b55b0cfd0cd39b5.zip | |
HID: playstation: Center initial joystick axes to prevent spurious events
[ Upstream commit e9143268d259d98e111a649affa061acb8e13c5b ]
When a new PlayStation gamepad (DualShock 4 or DualSense) is initialized,
the input subsystem sets the default value for its absolute axes (e.g.,
ABS_X, ABS_Y) to 0.
However, the hardware's actual neutral/resting state for these joysticks
is 128 (0x80). This creates a mismatch.
When the first HID report arrives from the device, the driver sees the
resting value of 128. The kernel compares this to its initial state of 0
and incorrectly interprets this as a delta (0 -> 128). Consequently, it
generates EV_ABS events for this initial, non-existent movement.
This behavior can fail userspace 'sanity check' tests (e.g., in
Android CTS) that correctly assert no motion events should be generated
from a device that is already at rest.
This patch fixes the issue by explicitly setting the initial value of the
main joystick axes (e.g., ABS_X, ABS_Y, ABS_RX, ABS_RY) to 128 (0x80)
in the common ps_gamepad_create() function.
This aligns the kernel's initial state with the hardware's expected
neutral state, ensuring that the first report (at 128) produces no
delta and thus, no spurious event.
Signed-off-by: Siarhei Vishniakou <svv@google.com>
Reviewed-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/hid/hid-playstation.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/hid/hid-playstation.c b/drivers/hid/hid-playstation.c index 2228f6e4ba23..38d5171dd25b 100644 --- a/drivers/hid/hid-playstation.c +++ b/drivers/hid/hid-playstation.c @@ -487,11 +487,16 @@ static struct input_dev *ps_gamepad_create(struct hid_device *hdev, if (IS_ERR(gamepad)) return ERR_CAST(gamepad); + /* Set initial resting state for joysticks to 128 (center) */ input_set_abs_params(gamepad, ABS_X, 0, 255, 0, 0); + gamepad->absinfo[ABS_X].value = 128; input_set_abs_params(gamepad, ABS_Y, 0, 255, 0, 0); + gamepad->absinfo[ABS_Y].value = 128; input_set_abs_params(gamepad, ABS_Z, 0, 255, 0, 0); input_set_abs_params(gamepad, ABS_RX, 0, 255, 0, 0); + gamepad->absinfo[ABS_RX].value = 128; input_set_abs_params(gamepad, ABS_RY, 0, 255, 0, 0); + gamepad->absinfo[ABS_RY].value = 128; input_set_abs_params(gamepad, ABS_RZ, 0, 255, 0, 0); input_set_abs_params(gamepad, ABS_HAT0X, -1, 1, 0, 0); |