Bug 254186 - skanlite's “Reload devices list” does not work
Summary: skanlite's “Reload devices list” does not work
Status: RESOLVED UPSTREAM
Alias: None
Product: Skanlite
Classification: Applications
Component: general (show other bugs)
Version: unspecified
Platform: Ubuntu Linux
: NOR normal
Target Milestone: ---
Assignee: Kåre Särs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2010-10-14 19:59 UTC by Bastian Senst
Modified: 2022-10-14 13:08 UTC (History)
2 users (show)

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Description Bastian Senst 2010-10-14 19:59:37 UTC
Version:           unspecified
OS:                Linux



Reproducible: Always

Steps to Reproduce:
* Disconnect your scanner from your computer.
* start up skanlite
* wait until he says: “Sorry. No devices found.”
* connect your scanner to your computer
* click on “Reload devices list”

Actual Results:  
Skanlite shows again “Sorry. No devices found.”

Expected Results:  
Skanlite recognizes the scanner.

This happens in version 0.4 from the Kubuntu 10.10 packages.
Comment 1 Kåre Särs 2010-10-15 07:53:40 UTC
Thanks,

This is unfortunately a known problem with some common sane backends :(

I have reported the problem to the sane list, but due to lack of time and man power they have not fixed it (yet?).

Technical explanation: The backends should probe for new devices whenever sane_get_devices() is called, but most of them only probe at sane_init(). Calling sane_init() will invalidate any already initialized instance.

I'm leaving this open as I have an idea of how to workaround this, but only when no device is opened...
Comment 2 Kåre Särs 2011-02-23 21:29:08 UTC
The sane developers preferred a proper fix in sane in stead of a workaround.

I'll mark this as an upstream problem.
Comment 3 H.H. 2015-07-09 13:28:24 UTC
this is still a problem, where is the upstream bug report?
Comment 4 Tobias Leupold 2022-10-14 11:55:08 UTC
I was just about to open a KSaneCore bug about this exact issue (by the way, there's no KSaneCore product yet in Bugzilla!).

This bug is 12 years old(!), but the behavior is still the same (of course no matter if you use Skanlite or some other program using KSaneCore as it's SANE backend). Calling KSane::CoreInterface::reloadDevicesList() only works when being called for the first time. Calling it again does not expose scanners attached in the meantime. Restarting the respective program makes the scanner(s) appear.

Tested with:
 - Brother DS-640 (using Brother's proprietary brscan5 backend)
 - Canon CanoScan LiDE 25 (using SANE's plustek backend)

Is there anything going on about this?! Is there some upstream bug filed/still open?
Comment 5 Kåre Särs 2022-10-14 13:08:21 UTC
The problem is still the same as in comment 1. The problems have not been fixed in backends :(

So after more than 10 years, maybe it would be time to actually do a workaround..., but the only current workaround makes it impossible to open multiple devices from one process..... on the other hand I do not know about any application that would open more than one device at a time...