[cups.general] Unable to print to USB

Johannes Meixner jsmeix at suse.de
Wed Feb 24 01:48:52 PST 2010


Hello Tim,

On Feb 24 09:13 Tim Waugh wrote (shortened):

> On Wed, 2010-02-24 at 09:44 +0100, Johannes Meixner wrote:
>> In contrast to the "hp" backend which privides bidirectional
>> communication (e.g. for scanning and for device status info)
>> the generic CUPS "usb" backend does only unidirectional
>> data transfer to the printer so that device status information
>> and scanning for HP all-in-one devices is no longer possible
>> with the generic CUPS "usb" backend,
>
> This isn't really true,

Yes I know that also the generic CUPS "usb" backend privides
bidirectional communication but not the kind of bidirectional
communication which I actually meant here.

> it's just that the HPLIP *filter* doesn't use
> the back-channel facility.  It should use the back-channel
> facility (all it needs is the IEEE 1284 Device ID actually),
> and then we won't need the hp backend any more.

Scanning with the hpaio SANE driver via the CUPS back-channel?

If I remember correctly, the "hp" backend implements
the 1284.4/MLC channel which is used both for printing
and scanning - but I am really no expert here.

As far as I understand it, there must be some kind of "multiplexer"
to deal with the different kind of data streams for HP all-in-one
devices like printing, scanning, faxing, mass-storage-access,...
and as far as I understand it, the "hp" backend implements this.

Therefore - as far as I understand it - even if the HPLIP filter
would use the CUPS back-channel for printer status info, it would
not work to use the generic CUPS "usb" backend for printing
while the hpaio SANE driver can still be used for scanning.


Kind Regards
Johannes Meixner
-- 
SUSE LINUX Products GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany
AG Nuernberg, HRB 16746, GF: Markus Rex





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