[sane-devel] When to disable sane?

[Ralph Little]

Hi,

On Mon, Feb 28, 2022 at 7:05 AM steve rinsler <stevesr0 at yahoo.com> wrote:

> Hi Ralph,
> My now my questions are (1) with the sane daemon disabled, what sane
> software is involved in scanning?
>

So the architecture is SANE frontend (this is your application, typically
scanimage, xsane or simple-scan) which loads SANE backends (DLLs which
provide support for classes of scanners via USB and Ethernet, such as
sane-genesys or sane-escl).

Many backends are part of the SANE project and you would typically find
them in /usr/lib/sane (exact location depends on your distro and arch).
However, there are 3rd party backends such as sane-airscan (which is free)
and brscan1/2/3 from Brother. These are installed in locations where SANE
frontends can find them in addition to the classic ones. They interact with
your frontend in the same way. Brother's backends offer access directly to
the network for network connectivity and also via USB depending on how you
have connected them. If you connect your Brother MFP to the router, then it
should be accessible and reachable by SANE on any PC that has SANE and the
Brother backend installed.

How the backend module *finds* the scanner really depends on the
implementation. Often network backends will probe for supported scanners by
using a variety of methods. I have seen some 3rd party backends come with a
utility that performs the probe or requests networking details (such as the
static IP) of the scanner via a GUI. Typically probes don't work if the
scanner is on another subnet and you have to supply some details directly.
This would usually be squirreled away into a config file somewhere for the
backend to find. The advantage of this is that startup is fast. Probing is
slow.

That's the long answer. The short answer is if the Brother machine is
network accessible to the PC and the Brother packages and SANE is
installed, then you should be able to scan. No saned is required.

saned is actually quite niche solution for most people and is useful only
for putting a non-networked scanner (e.g. USB only) onto the network for
other PCs to use.


> and (2) (BIG QUESTION) - “How to I figure out what is wrong on the
> computer that doesn’t (yet) successfully scan?
>
>
First I would remove-purge/reinstall the Brother software packages onto the
machine that won't scan. The scanner software for your machine is brscan3.
If you look to the bottom of the download page:

https://support.brother.com/g/b/downloadhowto.aspx?c=ca&lang=en&prod=mfc7340_us_as&os=128&dlid=dlf006642_000&flang=4&type3=566

...you can see instructions for running brsaneconfig3 to "register" your
machine. I guess that probably just drops some details into a config file
somewhere.
Now you should be able to find the scanner on the network with:

scanimage -L

If you are still not seeing it, try:

SANE_DEBUG_DLL=4 scanimage -L

...to see if you see the driver being loaded:

...
[09:11:14.207264] [dll] add_backend: adding backend `xerox_mfp'
[09:11:14.207292] [dll] add_backend: adding backend `brother4'
[09:11:14.207320] [dll] add_backend: adding backend `brother3'
[09:11:14.207376] [dll] sane_get_devices
...

Cheers,
Ralph
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