linux-kernel - [PATCH 01/10] HID: pidff: Convert infinite length from Linux API to PID standard

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Message-ID: <20241231154731.1719919-2-tomasz.pakula.oficjalny@gmail.com>
Date: Tue, 31 Dec 2024 16:47:22 +0100
From: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>
To: jikos@...nel.org,
	bentiss@...nel.org
Cc: linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	oleg@...arenk.ooo,
	paul@...cefreak18.xyz,
	f.kardame@...jaro.org,
	jules.noirant@...nge.fr
Subject: [PATCH 01/10] HID: pidff: Convert infinite length from Linux API to PID standard

Linux defines 0 length as infinite in its force feedback API
while USB PID defines NULL (0xffff). Most PID devices do not expect a
0-length effect and can't interpret it as infinite. This change fixes
Force Feedback for most PID compliant devices.

As most games depend on updating the values of already playing infinite
effects, this is crucial to ensure they will actually work.

Previously, users had to rely on third-party software to do this conversion
and make their PID devices usable.

Co-developed-by: Makarenko Oleg <oleg@...arenk.ooo>
Signed-off-by: Makarenko Oleg <oleg@...arenk.ooo>
Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>
---
 drivers/hid/usbhid/hid-pidff.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/usbhid/hid-pidff.c b/drivers/hid/usbhid/hid-pidff.c
index 3b4ee21cd811..1b5d3db62c09 100644
--- a/drivers/hid/usbhid/hid-pidff.c
+++ b/drivers/hid/usbhid/hid-pidff.c
@@ -301,7 +301,12 @@ static void pidff_set_effect_report(struct pidff_device *pidff,
 		pidff->block_load[PID_EFFECT_BLOCK_INDEX].value[0];
 	pidff->set_effect_type->value[0] =
 		pidff->create_new_effect_type->value[0];
-	pidff->set_effect[PID_DURATION].value[0] = effect->replay.length;
+
+	// Convert infinite lenght from Linux API (0)
+	// to PID standard (NULL) if needed
+	pidff->set_effect[PID_DURATION].value[0] =
+		effect->replay.length == 0 ? 0xffff : effect->replay.length;
+
 	pidff->set_effect[PID_TRIGGER_BUTTON].value[0] = effect->trigger.button;
 	pidff->set_effect[PID_TRIGGER_REPEAT_INT].value[0] =
 		effect->trigger.interval;
-- 
2.47.1