[boffinAudio]

Cool, got any suggestions for products that already implement this, particularly those with existing software shims that could be easily integrated into a test suite? I'd be a happy customer if there were such a thing, easily orderable, but I confess I don't quite know what keywords to use to find it ..

[seba_dos1]

"already"? It's something available since USB 1.0 has been created (see section 11.10). For example, it can be automatically used by the Linux kernel (after setting pm_qos_no_power_off to 0), and recently a node to disable a port explicitly has been added as well.

The support for commands themselves (SET/CLEAR_FEATURE) is mandated by the spec, so all hubs support it. However, some hubs don't feature port power control at all (are physically unable to selectively turn off power - you can only turn them all off or not at all), but for those it doesn't matter how you control them ;)