[sane-devel] Color managment `colord-sane` on Ubuntu 20.04 switches off USB-Port

[m. allan noah]

On Sat, Nov 2, 2024 at 10:00 AM Ulf Zibis via sane-devel <
sane-devel at alioth-lists.debian.net> wrote:

>
> I have the slide scanner "Braun MultiMag SlideScan 6000" here. When I
> connect it, the process `colord-sane` is started during its approx.
> 3-minute self-calibration, which then disappears again. After that, the
> device is no longer listed via `lsusb`, so presumably the USB port is
> switched off. During the 3 minutes it is still there:
> ...
>
> I use the VueScan program to use the scanner. If I start it during or
> after self-calibration, the scanner is not found
>
> The only way to connect VueScan to the scanner and then use it is to
> connect the scanner to USB only after self-calibration. However, this
> obviously prevents the use of colour management. What consequences could
> this have?
>
> In my humble opinion, it should not be the task of the SANE colour
> management to switch off USB ports.
> Could this be a bug? How can this be prevented?
>

You have made some assumptions here-

I don't see evidence that the port is switched off. This could just as
easily be the device getting into a state where it no longer talks to the
USB, perhaps because it was sent a command it does not understand. What
does `dmesg` say after the calibration is over?

Also, we are not the authors of colord-sane, that comes with colord. Can
you get it to show you some logging of what it is doing? If you disable or
uninstall it, does the behavior change?

In addition, I think that you should be able to use color profiles even if
you plug the scanner in after self calibration.

allan
-- 
"well, I stand up next to a mountain- and I chop it down with the edge of
my hand"
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://alioth-lists.debian.net/pipermail/sane-devel/attachments/20241102/f1adfe82/attachment.htm>