Re: [hpoj-devel] some port of PML to ptal

[<pa...@rc...>]

Jarl Friis wrote:
> I have ported some of the PML stuff to the ptal API.
> 
> until now I have ported getValue and setvalue, they are not thoroughly
> tested, but I can get the LCD lines at least :-) porting xojpanel..???
Hi, Jarl.  I've actually done a lot of this work already (adding PML
support to PTAL).  I'm using a different design from ojlib, so I started
from scratch rather than porting ojlib code, just as I did with PTAL itself.

> I was considering if it were best placed in ptal-mlc.c or maybe even
> a new ptal-mlc-pml.c, currenctly its a mix of pml.c and ptal.c
My overall philosophy for PTAL, which I continued when adding PML support,
is to have the generic interface and common implementation in ptal.c,
MLC-specific implementation in ptal-mlc.c, and JetDirect-specific
implementation in ptal-hpjd.c.  That way, the differences in accessing
PC- and JetDirect-connected peripherals are hidden from applications which
use PTAL.

> I do not have the time to continue the development in January, but I might
> do something in February, hope the code is good for soemthing, at least
> inspiration :-)
I got distracted from this lately dealing with I/O and printing issues in
preparation for releasing 0.7, and I'll try to get back to it within the
next couple of weeks.

> There are some open question:
> 1)What are the TWO bytes in the begining of PML values of type String?
The symbol set (character set) identifier.

> 2)How are the THREE bytes of errorcode (after the exec_code byte) supposed
> to be interpreted when such are sent as a reply?
According to the PML spec (which you can get by registering for a free
membership at http://www.hp-developer-solutions.com), these three bytes are:
0x18 (ErrorCodeDataType)
0x01 (constant)
0x?? (ErrorValue, for example 0x83=ErrorUnknownObjectIdentifier)

> Does anyone know anything about the PML error codes that can turnup in
> request responses?
> Has it anything to do with the ones found on HP help page:
> http://www.hp.com/cposupport/multifunction/support_doc/bpu50364.html
Those are firmware assert (panic) codes which indicate serious hardware
failures or firmware bugs and are completely unrelated to the error codes
defined by the PML protocol.

> I am currently working on adding the PML to the ptal, and I discovered
> that the PML oids on the web are not the same as in the
> ojlib/pmloidentries.c the difference are (at least) the two folloing
> objects:
I plan to significantly rewrite the web-based documentation once I finish
obsoleting ojlib and (if everything goes well) ieee12844*.c.  In addition,
I want to avoid coding knowledge of specific OIDs at the PTAL level, so
the centralized OID table will either go away or move somewhere else in
the codebase.

(BTW, it's not necessary for people to CC me on messages they send to the
mailing list.  I CC myself when sending messages just to make sure I have
a copy of it in case it gets lost or delayed.)

David