[sane-devel] As instructed by /etc/udev/rules.d/libsane.rules

[Johannes Meixner]

Hello,

On Nov 19 17:40 Richard Ryniker wrote (shortened):
> Udev rules are never likely to be a "stable interface".  Hardware
> devices and connection mechanisms change over time, therefore new and
> different information will be produced

I forgot to mention that it is always possible to
add new stuff to an existing stable interface
provided the new stuff is not mandatory and strictly
separated from the existing stuff (i.e. it works also
without the new stuff and does not interfere).

> the events recognized and
> reported may change as the kernel's structure evolves;

This is my complaint.
A stable interface does not change when the underlying
stuff changes - otherwise it is just no interface at all
but only a dumb "pass-through" of the underlying stuff.


> Your suggestion to have a user-oriented application that manipulates
> udev rules is sensible, though the same factors that force changes in
> udev semantics will likely mean this application also changes, albeit
> in a more controlled way from the perspective of the user.

Exactly!
Strictly speaking without such a tool udev has no user
interface at all and all what we currently do is
nothing else but evil hacks inside the internals of udev.

> I think SANE is not the right place to develop a udev
> rules-manipulation application.

Of course not!
It is udev which must provide a user interface for udev
or udev must provide a stable interface so that others
can make a user interface for udev.

> It is surprising that such an application has not already been
> written.

It is not surprising because udev does not provide the
precondition "stable interface" so that others cannot
make a user interface for udev.

> Perhaps
> some have tried, but failed because udev information and requirements
> changed faster than they could adapt their code.

q.e.d.

All who try to work with udev (i.e. all udev users) fail
because of this so that udev is a useless piece of software.
If it works it might even do some useful stuff in the system
but this is not what I mean with "useful software" here.
It is a useless piece of software because nobody can use it
simply because udev has currently no user interface.


Kind Regards
Johannes Meixner
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