linux-kernel - [PATCH 02/10] HID: pidff: Do not send effect envelope if it's empty

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Message-ID: <20241231154731.1719919-3-tomasz.pakula.oficjalny@gmail.com>
Date: Tue, 31 Dec 2024 16:47:23 +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 02/10] HID: pidff: Do not send effect envelope if it's empty

Envelope struct is always initialized, but the envelope itself is
optional as described in USB PID Device class definition 1.0.

5.1.1.1 Type Specific Block Offsets
...
4) Effects that do not use Condition Blocks use 1 Parameter Block and
an *optional* Envelope Block.

Sending out "empty" envelope breaks force feedback on some devices with
games that use SINE effect + offset to emulate constant force effect, as
well as generally breaking Constant/Periodic effects. One of the affected
brands is Moza Racing.

This change prevents the envelope from being sent if it contains all
0 values while keeping the old behavior of only sending it, if it differs
from the old one.

Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>
---
 drivers/hid/usbhid/hid-pidff.c | 39 ++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/drivers/hid/usbhid/hid-pidff.c b/drivers/hid/usbhid/hid-pidff.c
index 1b5d3db62c09..e78fd68edda3 100644
--- a/drivers/hid/usbhid/hid-pidff.c
+++ b/drivers/hid/usbhid/hid-pidff.c
@@ -261,10 +261,19 @@ static void pidff_set_envelope_report(struct pidff_device *pidff,
 static int pidff_needs_set_envelope(struct ff_envelope *envelope,
 				    struct ff_envelope *old)
 {
-	return envelope->attack_level != old->attack_level ||
-	       envelope->fade_level != old->fade_level ||
+	bool needs_new_envelope;
+	needs_new_envelope = envelope->attack_level  != 0 ||
+		             envelope->fade_level    != 0 ||
+		             envelope->attack_length != 0 ||
+		             envelope->fade_length   != 0;
+
+	if (!needs_new_envelope || !old)
+		return needs_new_envelope;
+
+	return envelope->attack_level  != old->attack_level  ||
+	       envelope->fade_level    != old->fade_level    ||
 	       envelope->attack_length != old->attack_length ||
-	       envelope->fade_length != old->fade_length;
+	       envelope->fade_length   != old->fade_length;
 }
 
 /*
@@ -579,11 +588,9 @@ static int pidff_upload_effect(struct input_dev *dev, struct ff_effect *effect,
 			pidff_set_effect_report(pidff, effect);
 		if (!old || pidff_needs_set_constant(effect, old))
 			pidff_set_constant_force_report(pidff, effect);
-		if (!old ||
-		    pidff_needs_set_envelope(&effect->u.constant.envelope,
-					&old->u.constant.envelope))
-			pidff_set_envelope_report(pidff,
-					&effect->u.constant.envelope);
+		if (pidff_needs_set_envelope(&effect->u.constant.envelope,
+					     &old->u.constant.envelope))
+			pidff_set_envelope_report(pidff, &effect->u.constant.envelope);
 		break;
 
 	case FF_PERIODIC:
@@ -618,11 +625,9 @@ static int pidff_upload_effect(struct input_dev *dev, struct ff_effect *effect,
 			pidff_set_effect_report(pidff, effect);
 		if (!old || pidff_needs_set_periodic(effect, old))
 			pidff_set_periodic_report(pidff, effect);
-		if (!old ||
-		    pidff_needs_set_envelope(&effect->u.periodic.envelope,
-					&old->u.periodic.envelope))
-			pidff_set_envelope_report(pidff,
-					&effect->u.periodic.envelope);
+		if (pidff_needs_set_envelope(&effect->u.periodic.envelope,
+					     &old->u.periodic.envelope))
+			pidff_set_envelope_report(pidff, &effect->u.periodic.envelope);
 		break;
 
 	case FF_RAMP:
@@ -636,11 +641,9 @@ static int pidff_upload_effect(struct input_dev *dev, struct ff_effect *effect,
 			pidff_set_effect_report(pidff, effect);
 		if (!old || pidff_needs_set_ramp(effect, old))
 			pidff_set_ramp_force_report(pidff, effect);
-		if (!old ||
-		    pidff_needs_set_envelope(&effect->u.ramp.envelope,
-					&old->u.ramp.envelope))
-			pidff_set_envelope_report(pidff,
-					&effect->u.ramp.envelope);
+		if (pidff_needs_set_envelope(&effect->u.ramp.envelope,
+					     &old->u.ramp.envelope))
+			pidff_set_envelope_report(pidff, &effect->u.ramp.envelope);
 		break;
 
 	case FF_SPRING:
-- 
2.47.1