From: Oliver Neukum <oliver@neukum.org>
Organization: Novell
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Subject: Re: [PATCH] PNPACPI: Enable Power Support
Date: Wed, 10 Dec 2008 11:22:59 +0100
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Cc: Witold Szczeponik <Witold.Szczeponik@gmx.net>, linux-acpi@vger.kernel.org,
       linux-kernel@vger.kernel.org, Bjorn Helgaas <bjorn.helgaas@hp.com>,
       Adam Belay <abelay@mit.edu>, rjw@sisk.pl
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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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