RE: [hpoj-devel] USB Cold Plug Etc.

[PASCHAL,DAVID (HP-Roseville,ex1) <dav...@hp...>]

Hi, Allen.

Allen Barnett wrote:
> I cold started my machine this morning and was surprised to 
> see that the
> USB printer.o module was not 'cold plugged' as the machine 
> booted. If I
> pull the USB plug and reinsert it, the printer.o module is 
> loaded OK (by
> /sbin/hotplug?), after which ptal-mlc and ptal-printd can be 
> started OK.
> Is there a patch to the USB printer.c module for the G85 (or similar)
> which can cause it to be loaded at boot time? (There's some 
> info in the
> hotplug README about using the 'usbmodules' command if a module is not
> loading at boot time. Is this the way to go?)
I don't think the problem is in printer.c.  The "hot-plugging" section of
the FAQ page at http://www.linux-usb.org mentions the term "cold-plugging",
which is what you're having a problem with, but I can't find any specific
information about it.  It sounds like you're reading the right information,
though, so run whatever commands you need to in order to make it work.  :-)
I personally avoid the whole mess by insmoding all the necessary modules at
startup.

> I was also wondering what the status of FAXing to and from 
> the PC. Soon?
> Possible?
As far as I know, fax-receive isn't supported in the G or K series firmware,
so it won't be possible to support it in software either (but fax-send is
possible).  I need to finish implementing PML (see below) before I can
implement broader scanning support or faxing/copying support where possible.
I may provide some quick-and-dirty PML scanning/faxing/copying utilities to
help test the PML support and get that functionality working before I start
writing a fancier implementation.

> I was also wondering about the 'Scan To' button on the front 
> panel. Can
> this be programmed?
Theoretically yes, but I'll have to do some research to find out exactly how
to do it.  I do know it involves PML, especially PML traps.

> And yet another dumb question: what are 'PML' and 'MFPDTF' 
> mentioned on
> the TODO page at hpoj.sourceforge.net?
Not a dumb question at all.  I should explain it better on the web.  PML
stands for Peripheral Management Language, and is a datagram request/reply
management protocol similar to SNMP.  xojpanel (currently disabled in CVS)
uses PML to get the contents of the LCD.  Scanning (non-SCL), faxing, and
copying use PML to set various options, like color depth and resolution and
to start/stop the operation.  PML traps are a mechanism for the peripheral
to notify the host when the value of an object changes so the host doesn't
have to constantly poll.  MFPDTF stands for Multi-Function Peripheral Data
Transfer Format and defines a packet format for scan/fax/copy data.  There's
a small amount of information about these topics under the now outdated
documentation section on the web page.  If you're interested I can forward
you some more information provided by HP, with the stipulation that you
can't re-distribute the documents themselves.

David