Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752133AbaJKWZO (ORCPT ); Sat, 11 Oct 2014 18:25:14 -0400 Received: from icebox.esperi.org.uk ([81.187.191.129]:49314 "EHLO mail.esperi.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbaJKWZM (ORCPT ); Sat, 11 Oct 2014 18:25:12 -0400 From: Nix To: Paul Martin Cc: Oliver Neukum , Johan Hovold , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: Re: [3.16.1 BISECTED REGRESSION]: Simtec Entropy Key (cdc-acm) broken in 3.16 References: <878um4tg09.fsf@spindle.srvr.nix> <1409569752.24385.12.camel@linux-fkkt.site> <874mwnosz1.fsf@spindle.srvr.nix> <871tqe2zqt.fsf_-_@spindle.srvr.nix> <20141011195108.GA8275@thinkpad.nowster.org.uk> Emacs: a Lisp interpreter masquerading as ... a Lisp interpreter! Date: Sat, 11 Oct 2014 23:24:59 +0100 In-Reply-To: <20141011195108.GA8275@thinkpad.nowster.org.uk> (Paul Martin's message of "Sat, 11 Oct 2014 20:51:08 +0100") Message-ID: <87y4smz1l0.fsf@spindle.srvr.nix> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-DCC-wuwien-Metrics: spindle 1290; Body=5 Fuz1=5 Fuz2=5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11 Oct 2014, Paul Martin spake thusly: > Having been privy to the firmware of the eKey, it is very simplisting, > with no implementation whatsoever of any flow control. That's what I thought. (Why would something that just provides data at a constant rate way below that of even the slowest USB bus *need* flow control?) One presumes therefore that the kernel suddenly trying to do flow control on shutdown would fubar the firmware's internal state, leading to the symptoms I see. So, the question becomes, is there a way to spot this general 'no flow control on this device' thing from the kernel side, or do we need a blacklist? Or, perhaps, if this is commonplace for cdc-acm devices, a whitelist? I can't imagine it's *that* commonplace or someone would have spotted this already in the months and months it took me to do the bisection. Maybe all non-modem cdc-acm devices should eschew flow control, or something? (This is a genuine guess and is almost certainly wrong.) -- NULL && (void) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/