[cups-devel] requested-attributes: IPP_TAG_NAME versus IPP_TAG_KEYWORD

[Michael Sweet]

Johannes,

> On Feb 5, 2015, at 12:02 PM, Johannes Meixner <jsmeix at suse.de> wrote:
> 
> 
> Hello Michael Sweet
> and Till Kamppeter,
> 
> I noticed that in some (curently rare) cases
>  ippAddStrings(... IPP_TAG_NAME, "requested-attributes" ...)
> is used instead of the correct form
>  ippAddStrings(... IPP_TAG_KEYWORD, "requested-attributes" ...)
> ...
> I would like to find out if my fear is founded
> or if it is only an unfortunate coincidence.

This is probably a combination of code sharing and cupsd's prior leniency regarding the value type for the "requested-attributes" request attribute.

> When it is used falsely in a request to the cupsd, it results that
> only a small subset of values is returned in cupsd's response
> which causes unexpected strange behaviour of the application
> that uses it falsely in its request.

Right - this is a side effect of actually conforming to IPP/1.1's rules for Get-Jobs.

> ...
> I would like to know what change in CUPS 1.3.9 versus CUPS 1.7.5
> makes 'IPP_TAG_NAME, "requested-attributes"' no longer work.

This was changed in CUPS 1.4 as part of adding IPP Everywhere support and fixing a bunch of conformance problems.

> As far as we found out the 'IPP_TAG_NAME, "requested-attributes"'
> in Samba came from Michael Sweet in 2003 according to
> https://lists.samba.org/archive/samba-technical/2003-January/026577.html

Yeah, and I probably copied that from the cups/util.c code for cupsGetJobs, which had the same problem (a while back).

> What makes me a bit nervous is that in 2013 Till Kamppeter still
> had used 'IPP_TAG_NAME, "requested-attributes"' which may indicate
> that there is perhaps wrong documentation somewhere?

No, just a lack of reading the available documentation (which I'll grant is a lot to do...)

_________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair