Re: Break not functioning on pl2303 serial adaptor

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On Thu, Nov 03, 2011 at 11:46:48AM -0400, Nick Bowler wrote:
> On 2011-11-03 08:35 -0700, Greg KH wrote:
> > On Thu, Nov 03, 2011 at 10:47:16AM -0400, Nick Bowler wrote:
> > >   pl2303_break_ctl - error sending break = -32
> > > 
> > > -32 would appear to be EPIPE.  With the debugging disabled these errors
> > > get dropped on the floor, hence everything seems normal except that
> > > nothing happens when I send a break.  The adaptor seems to work
> > > fine otherwise.
> > 
> > That means your device does not support the "set break" command, sorry.
> > 
> > I suggest you use a "real" usb to serial device, and not this one, if
> > you need to send a break with it.  The pl2303 device is barely a
> > workable serial device, in my opinion of working with it for years.
> > There are many other better devices out there (like the ftdi_sio
> > devices for one.)
> 
> OK, fair enough.
> 
> 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.

Do you see any other -32 messages in the kernel log for this device?
Something seems really wrong here.

> Is there a way to send sysrq commands over a serial console without
> using break?

You can echo the command you want to the proper proc file.  See the
file, Documentation/sysrq.txt for details.

greg k-h
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