From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750966AbWFAXhK (ORCPT ); Thu, 1 Jun 2006 19:37:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750968AbWFAXhK (ORCPT ); Thu, 1 Jun 2006 19:37:10 -0400 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:27974 "EHLO pd2mo2so.prod.shaw.ca") by vger.kernel.org with ESMTP id S1750958AbWFAXhI (ORCPT ); Thu, 1 Jun 2006 19:37:08 -0400 Date: Thu, 01 Jun 2006 17:37:01 -0600 From: Robert Hancock Subject: Re: USB devices fail unnecessarily on unpowered hubs In-reply-to: <6iYQx-5Jc-7@gated-at.bofh.it> To: linux-kernel Cc: Alan Stern Message-id: <447F7A1D.3070906@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: <6iYGP-5hv-3@gated-at.bofh.it> <6iYQx-5Jc-7@gated-at.bofh.it> User-Agent: Thunderbird 1.5.0.2 (Windows/20060308) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Alan Stern wrote: >> >> (Goes away and pats all his 240V plugpacks which are happily working off 110V). > > They probably will. The question is, how far out-of-spec should the > kernel allow by default? 200% is likely to be too far (your plugpacks > notwithstanding). I would say by default the kernel should not allow any out-of-spec power condition. Some devices might decide to go into over-current mode if a device draws too much power, taking down other devices on the USB bus. This sort of behavior should only be enabled if the user explicitly chooses to live dangerously. Especially given the fact that Windows enforces the USB power supply limits strictly, and that's where all the hardware is best tested.. -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/