Re: Break not functioning on pl2303 serial adaptor

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On 2011-11-03 09:12 -0700, Greg KH wrote:
> On Thu, Nov 03, 2011 at 12:10:50PM -0400, Alan Stern wrote:
> > On Thu, 3 Nov 2011, Greg KH wrote:
> > > > Perhaps this driver could print an error message to that effect, then,
> > > > instead of remaining completely silent?  If EPIPE means "not supported",
> > > > I can cook something up.
> > > 
> > > Wait, -EPIPE is odd, that usually means the driver messed up in trying
> > > to send a message to the wrong endpoint.  Yet this is going through the
> > > control endpoint, which really can't fail.
> > 
> > -EPIPE also means that the control endpoint doesn't recognize the 
> > command it received, which seems quite likely in this case.
[...]
> So, this makes sense, this device has no idea how to create a BREAK
> command, not much we can do about it, especially given the total lack of
> documentation from Prolific for this chipset.
> 
> Again, I recommend buying a new device.

I agree that is the most prudent course.  sysrq-trigger isn't really an
option because the situations where I want to send sysrq commands over
the serial port are usually the same situations where logging into the
machine is impossible.

Nevertheless, I'll cook a patch to add an error message, because
silently doing nothing is not really helpful.

Thanks,
-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)
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