On 19.01.25 14:12, Tomasz Pakuła wrote:
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.
[..]
@@ -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;
I am afraid this is the most convoluted piece of boolean algebra I've seen
in a long time. In particular because it mixes things that do not belong together.
Regards
Oliver
