Re: [PATCH] PNPACPI: Enable Power Support

[Oliver Neukum]

Am Mittwoch, 10. Dezember 2008 10:53:15 schrieb Henrique de Moraes Holschuh:
> Although I do wonder WTF we don't do that on our USB UHCI/EHCI kernel
> drivers, that ACPI needs to step in to fix it.  If it is not a wake

EHCI/UHCI have no way to power down host controllers.
It needs external means, namely ACPI.

> device, why are we leaving it powered up?  It is bad enough we don't
> have any sort of proper USB power control, but to leave the entire USB
> subsystem powered up without reason?!

We don't. If you unplug all devices, USB will power down as much as is
compatible with detecting new devices.

> Vista not only powers down the USB HCIs and ports on STR, it also
> powers down ports when you "safely remove the USB device", and seems
> to leave the port powered down until you insert a device (or remove
> the device already in there, whatever).

If you cut power to a port, you cannot detect a hotplugging. You can
suspend it, which Linux does do.

	Regards
		Oliver



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