Re: Break not functioning on pl2303 serial adaptor

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On Thu, 3 Nov 2011, Greg KH wrote:

> 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.

-EPIPE also means that the control endpoint doesn't recognize the 
command it received, which seems quite likely in this case.

Alan Stern

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