Existing practice for embeddable IPP servers in printers

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Hi,

It is my understanding that, for newly-developed devices, it is standard fo=
r a printer to have an embedded microprocessor which runs an IPP daemon of =
some sort, and then the printer is operated using IPP (over a network or US=
B). It is also my understanding that the majority of those printers use pro=
prietary software internally, and in the absence of evidence otherwise, thi=
s probably includes the HTTP servers and/or IPP daemons they run on as well=
. The primary focus of OpenPrinting, CUPS, and friends seems to be running =
on a server or workstation to interface *with* a printer as a peripheral. I=
nformation about crafting and maintaining the software *inside* of a printe=
r seems much more scarce.

What's the current state of the art for a printer's internal software stack=
? Most OpenPrinting software doesn't appear to have been made with small mi=
crocontrollers (which may not have virtual memory) or real-time operating s=
ystems in mind, and I'm not sure it caters to this need anyway.
Many embedded operating systems that would make good candidates (Linux Foun=
dation's Zephyr, Eclipse's ThreadX [1], or Apache's Mynewt or NuttX) are ca=
pable of running HTTP servers without fuss. It's conceivable that an IPP se=
rvice could work by hooking into it with CGI or something like it. Is that =
something that's usually done with custom code, or do lightweight libraries=
 exist that help with processing jobs, parsing options, and the like? Is th=
ere any toolkit or library that helps in making small device-side IPP daemo=
ns, or is it something that isn't done with free software very often and th=
ere isn't much precedent for it?

Thanks,
John

[1] ThreadX is supposedly used by HP on some printers: https://www.ghs.com/=
customers/hp.html

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