cups cupsBackChannelRead

velupillai kalyani.vel at
Mon Jan 28 07:47:23 PST 2008

> velupillai wrote:
> > Hello,
> >
> > Thanks for your response.
> > It is the standard usb backend which is used.
> > We are working for the manufacturer of the USB Printer.
> > We have developed driver (The printing is working -- But we cannot receive the status)
> > To Get the status we have to send a request. We do that directly in the data flow.
> > The Printer sends a response (one byte) which is received by the backEnd
> > (trace "Received 1 bytes of back-channel data!")
> > We see in the sources that the Backend call "CupsBackchannelWrite"
> > (this function write in fd=3)
> >
> > In our process (ijsserver) we try to get the status Byte by calling
> > cupsBackChannelRead
> > _bytes = cupsBackChannelRead(_buffer,1, 0.0)) which return -1
> You can't read back-channel data from an IJS-based printer driver.
> You MUST use CUPS raster, as IJS does not pass the back (or side)
> channel file descriptors to the driver...

So How can we get the printer status ?
The backend receive the response (we verified it's the good one)
Now what can we do ?
Our IJS Server is already operational and delivered to our client.

Thank's in advance

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