From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Stuge Subject: Re: [RFC PATCH] usb/acpi: Add support usb port power off mechanism for device fixed on the motherboard Date: Fri, 11 May 2012 16:30:27 +0200 Message-ID: <20120511143027.8313.qmail@stuge.se> References: <20120511041309.22096.qmail@stuge.se> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alan Stern Cc: Sarah Sharp , Dan Williams , Lan Tianyu , lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-acpi@vger.kernel.org Alan Stern wrote: > > > Maybe we need an "off" setting that forces the port off? > > > > FWIW this would be very welcome in libusb, to do a hard reset of > > bus-powered devices. > > > > It can be attempted via SET_FEATURE(PORT_POWER) to the hub, but a > > "real" API would be nice. > > But remember that such an API would be very unreliable. Many hubs and > root hubs cannot shut off port power at all, and some of the remaining > ones use ganged power switches (you have to turn off all the ports in a > gang before power is removed from any of them). Yes, I know. It would be extra special nice if the kernel exposes these various capabilities, in case they are already known. //Peter -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html