Thanks a lot for your answers, you’ve saved me weeks of pointless struggle, and taught me much.
I have another device that could do the work, and is HID. Using it isn’t as clean as using the device initially at hand, but it still sounds like a possibility to me so far. Actually, the devices I am working with are controller adapters. I hardly care about the latency/responsiveness, I care about the fact that feeding data at 125Hz into a state-machine-like engine that updates at 60/120Hz creates discreet but very big problems, and I’m trying to fix these globally. The HID adapter polls every ~1,4ms as well but converts the data to a HID Controller format. I’ve yet to determine what the benefits of using a dedicated format are compared to using HID conversion, but that’s not the subject here.
This device also has an 8ms interval declared, however I am confused about whether HID obeys to the same rules. Considering this is a driver-level change and you’ve made it very clear intervals were enforced at HCD level, it shouldn’t solve the problem.
So what does HidUsbF do ? In https://community.osr.com/discussion/190849/usb-polling-rate , Tim, are you talking about HidUsbF ? Does that mean Cay Bremer’s answer is incorrect ? He mentions that it “allows users to customize the polling interval of USB mice and other HIDs” and “consists primarily of a lower-level filter driver to HidUsb”.
As for re-programming the endpoint descriptor on the hardware directly, it would be a partial victory, as the initial goal was to fix these problems for everyone, but a victory nonetheless. I had actually considered it and began looking elsewhere before the complexity of the task (and not having the tools), hoping to find a software-only way. I will resume looking this way if HID conversion doesn’t work out - and it doesn’t look like it’s going to. Looking at the device’s board (the original device), the only microcontroller in sight is a ST 32bits (is inscribed: 32LP151 C6NTO GH21E VG CHN 521). I don’t know if the security bit is set. But before asking any question on that subject, I’ll look more into how vendor-provided chip reprogramming works.