I have been meaning to add sane support to libferris since I upgraded my scanner to something modern. I now also have an Automatic Document Feeder (ADF) so naturally that needs to be a filesystem too. A quick example of how this might be useful, to turn a document into something on screen quickly:
$ fcat sane:///my-scanner/color/scan.jpg | okular -
The trees under sane:// allow preconfigured scanning units and discovery. If you have setup my-scanner then no device listing is performed with sane, a good thing because discovery can be slow. When you configure a scanner you create one or more directories with specific configurations of how you want the scan to proceed. Incidentally, configuration is of course done with a filesystem. Inside ~/.ferris/sane you create a directory for your scanner, plomp the device name into scanner/device and create directories with scanning options for that scanner.
As well as scan.jpg there is a directory "adf" which chomps new things from the ADF for each file you read. Having this directory allows you to grab 20 documents by a normal looking posix like command such as:
$ ferriscp -av sane:///adf/gray-100/adf /tmp/
in this case, I made two trees, color-N and gray-N which scan in color or grayscale at a given DPI (100,300,600 etc). So I can get most of what I want by picking the right directory. "adf" is a softlink to my scanner (a local link in ~/.ferris/sane from adf to "my-scanner"). Using links like this means I can replace the hardware and scripts can still just ask for "the adf" scanner and get something.
One might wonder what happens for a scanner which is not known to the system. The ".discovery" configuration inside ~/.ferris/sane provides defaults for such devices, so you can have your color/gray DPI directories magically appear for discovered scanners too. Of course, most of the gray directories are similar, so softlinks are your friend except for the "resolution" file which you want to change per directory.
Discovery isn't performed for the above commands, because libferris uses short cut directory loading as it knows explicitly how to make the virtual filesystems for preconfigured scanners.
Some hints on configuration will be in dot-ferris/sane/dot-discovered which will be in libferris 1.5.6+ along with the code to actually make it happen.