[sane-devel] Fwd: Ubuntu documentation

Steven Santos steven at simplycircus.com
Mon Jun 24 22:31:24 BST 2019

On Mon, Jun 24, 2019 at 9:04 AM Olaf Meeuwissen <paddy-hack at member.fsf.org>

> That bug report has also been reported against our backends project.
> See https://gitlab.com/sane-project/backends/issues/45
> BTW, a related Ubuntu bug reports is in
>   https://bugs.launchpad.net/ubuntu/+source/sane-backends/+bug/1707352 is
> I've only skimmed the first bug report (1728012) but it seems that a
> large number of third-party backend supported scanners stopped working
> when "artful" was released.  The bug reports starts with
>   Many scanners can no more be used since sane has changed something
> Fair enough, from zesty to artful, the SANE backends went from
>   zesty : libsane 1.0.25+git20150528-1ubuntu4
>   artful: libsane1 1.0.27-1~experimental2ubuntu1

The issue with libsane vs libsane1 seems to have been resolved.

> but we did *not* change any of those third-party backends.  More
> importantly, the dll backend did not change how it finds and loads any
> of the backends that are configured in dll.conf or dll.d/*.  Anyone can
> "easily" confirm this by inspecting the output of
>   git log  RELEASE_1_0_25..RELEASE_1_0_27 -- backend/dll.*
>   git diff RELEASE_1_0_25..RELEASE_1_0_27 -- backend/dll.*
> If third-party backends are no longer loaded by the dll backend (you can
> check with
>   SANE_DEBUG_DLL=5 scanimage -L
> what backends are and are not loaded), then that is *not* something that
> the sane-backends broke.

Let me be clear, we know other distros are using it without issue, so we
know its a ubuntu issue.  I even put that in the docs I wrote.

> It has everything to do with the directories
> where the dll backend looks but that is something that is configured by
> the distribution.  If the distribution stops looking where third-party
> backends have been installed for ages (that's called breaking backward
> compatibility), then that's the distribution's prerogative but it is
> also *their* task to sort out the resulting breakage that their users
> experience.

Well, I don't have control of that.  All I can do is write some
documentation to try and help :/

Of course, third-party also *should* follow the distributions they, eh,
> "support" and update their packages accordingly.  Ideally, they'd even
> reply to their users' support requests ...
> # Eh, that's assuming they even have a place you can contact them :-/

Brother updated brscan4 and 5, but not brscan, brscan1, brscan2 or
brscan3.  For those we still need the simlink and udev tricks.

> > On Sun, Jun 23, 2019 at 1:14 PM m. allan noah <kitno455 at gmail.com>
> wrote:
> >
> >> I don't know of any reason that a sane backend would require the
> >> firmware upload to be done as root. All of sane runs in user space.
> >> Can you please elaborate?
> All of SANE runs in user space all right, but whatever process tries to
> upload that firmware file still needs write privileges to wherever that
> scanner is located at.  Our SANE backends don't do anything tricky that
> I'm aware of and upload firmware from the same process as the frontend's
> but if a third-party "outsources" the upload to a separate process that
> might not have the required write privilege.
> It's a bit of a long shot, but I thought I'd mention it.

You may well be on to something. As I down own an affected scanner, any
idea how we can test this?  If this is the issue, it should be solvable
with either a udev or a group membership change.

# I know that some of the third-party non-free EPSON plugins load the
> # firmware from the plugin, which may be running in a separate process
> # (depending on the plugin, I don't really remember all the details).
> Other than that, from the bug report mentioned it looks like printer
> related udev rules may be clobbering third-party scanner rules (more
> likely so for all-in-one type devices).  To complicate matters further,
> the *distribution* *specific* sane-backends rules may clobber part of
> those printer rules yet again.
> Hope this helps,

Immensely!  Thank you!

Quite a bit of this has ended up in the ubuntu sane docs already.   The
SANE_DEBUG_DLL=5 scanimage -L command was also a great addition.

I'll keep writing as I see new developments.
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