Messages in this thread | | | Date | Sun, 12 Oct 2014 12:14:05 +0100 | From | Paul Martin <> | Subject | Re: [3.16.1 BISECTED REGRESSION]: Simtec Entropy Key (cdc-acm) broken in 3.16 |
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On Sat, Oct 11, 2014 at 11:24:59PM +0100, Nix wrote: > On 11 Oct 2014, Paul Martin spake thusly: > > > Having been privy to the firmware of the eKey, it is very simplistic, > > 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.) >
I'm going to pass this on to Daniel Silverstone, who did the actual coding of the firmware.
-- Paul Martin <pm@debian.org>
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