From: Nix <nix@esperi.org.uk>
To: Paul Martin <pm@debian.org>
Cc: Oliver Neukum <oliver@neukum.org>,
Johan Hovold <jhovold@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [3.16.1 BISECTED REGRESSION]: Simtec Entropy Key (cdc-acm) broken in 3.16
Date: Sat, 11 Oct 2014 23:24:59 +0100 [thread overview]
Message-ID: <87y4smz1l0.fsf@spindle.srvr.nix> (raw)
In-Reply-To: <20141011195108.GA8275@thinkpad.nowster.org.uk> (Paul Martin's message of "Sat, 11 Oct 2014 20:51:08 +0100")
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)
next prev parent reply other threads:[~2014-10-11 22:25 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-31 23:07 [3.16.1 " Nix
2014-09-01 11:09 ` Oliver Neukum
2014-09-04 23:40 ` Nix
2014-09-05 7:59 ` Oliver Neukum
2014-09-05 15:17 ` Nix
2014-09-08 7:21 ` Oliver Neukum
2014-09-08 7:58 ` Nix
2014-10-11 19:05 ` [3.16.1 BISECTED " Nix
2014-10-11 19:51 ` Paul Martin
2014-10-11 22:24 ` Nix [this message]
2014-10-12 11:14 ` Paul Martin
2014-10-12 18:58 ` Johan Hovold
2014-10-12 21:36 ` Nix
2014-10-14 8:34 ` Johan Hovold
2014-10-14 14:44 ` Nix
2014-10-17 13:21 ` Nix
2014-10-19 13:45 ` Johan Hovold
2014-10-22 9:31 ` Nix
2014-10-22 10:14 ` Johan Hovold
2014-10-22 14:00 ` Nix
2014-10-22 15:36 ` Nix
2014-10-24 11:14 ` Johan Hovold
2014-10-24 15:08 ` Nix
2014-10-31 16:44 ` Nix
2014-11-05 11:56 ` Johan Hovold
2014-11-05 15:14 ` Nix
2014-11-05 15:46 ` Daniel Silverstone
2014-11-05 18:14 ` Johan Hovold
2014-11-06 13:49 ` Nix
2014-11-06 17:04 ` Johan Hovold
2014-11-06 17:08 ` [PATCH] USB: cdc-acm: add quirk for control-line state requests Johan Hovold
2014-11-07 9:05 ` Oliver Neukum
2014-11-07 9:16 ` Johan Hovold
2014-11-07 10:23 ` Oliver Neukum
2014-11-06 17:14 ` [3.16.1 BISECTED REGRESSION]: Simtec Entropy Key (cdc-acm) broken in 3.16 Nix
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