Comment 99 for bug 35638

You said you have Thinkpad R51 That has a 25 pin parallel port on he back,
and your LaserJet4 printer has a Centronics port.

On Fri, Apr 11, 2008 at 4:32 PM, dracon <email address hidden> wrote:

> George, thanks.
>
> Since telling Windoze where the printer is was a one time deal, that isn't
> a problem on that side. Wish that could be done for Ubuntu.
> Parallel cables don't solve my problem of easily switching the printer off
> to my laptop either which has no Centronics port.
>
> Now to cups. I don't think this is really a cups problem but I don't yet
> really understand well the relationship between hal and cups. I'm under
> the impression that hal runs before cups. It seems that when hal has
> found and identified the devices' that exist (even if the identification
> is "unknown usb device") then cups is capable 1) of allowing driver to
> be assigned to that device/hal port and 2) follow that device if it is
> subsequently moved to another usb port between reboots.
>
> It's only when hal only finds the printer cable (Centronics parallel to
> usb cable device) and does not find a printer on the end of the cable
> (even a "unknown" printer) that cups does not present that printer for
> configuration in the "add Printer" options. That leads me to conclude
> that cups is ok but hal is not.
>
> Now I don't know what hal uses to get the hardware info but from what
> I've read hal is pretty low level stuff looking for signals on specific
> pins with certain timings...etc. Since hal has found the Cable device I
> expect that his timing is PDQ and he doesn't wait a long time for the
> end point (printer) of the cable to post a signal....Just guessing here
> but if hal moves on to the next port before whatever device is on the
> end of that cable sends a "i'm here!", he will not even find a "unknown"
> device and assumes that no device exists. At that point cups can't find
> a printer to configure since hal tells him there is no device on the
> cable.
>
> Net: I believe this could be a simple timing fix in hal for a coder to
> cause hal to wait a millisecond or so for the device at the cable end to
> post if he finds a Parallel2usb "Printer" cable device on the port (he
> can tell the difference), (but not me! unless I get sufficently bugged
> to go back to school -lol- not likely)
>
> I don't think this is a cups problem...(is problem for me though) If
> it's hal this problem will be distribution independent across Linuxes
> and while the older HP laserjets may be "older" there are a bunch out
> there, and this has more to do with how hal is handling the Parallel
> Printer Cable device regardless of manufacturer.. (I lose my HP 890c
> inkjet sometimes as well the same exact way...just not as often probably
> because it is quicker at responding to it's interface...and I've seen
> the problem expressed with Brother, Epson, and other printers of both
> technologies in several fora, not just this one. (most end with a null
> answer as this one seems to have))
>
> Any idea how to get a hal type to take a look at this? I guess Ubuntu
> team could champion it but the interest seems low even from the cups
> side. Still if Ubuntu is trying to establish itself in the laptop market
> where parallel ports are appearing less frequently maybe they should
> take a look at this.
>
> --
> Printer is not detected properly over USB
> https://bugs.launchpad.net/bugs/35638
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