[sane-devel] How o make genesys backend make use of symlink via udev-rule?

[Ralph Little]

Hi,

On 2021-08-06 3:55 p.m., Heinz Rohde wrote:
> Hello Ralph,
>
> it's quite easy: as I wrote, due to the limited capabilities of the 
> windows clients, I hav eto reinstall them every time the scanner geht 
> new bus/device ID which happens every time if you reset the server or 
> plug in/out the Scanner (which normally does not happen).
>
> In the latter, the windows clients keep their settings and are not 
> able to reconnect to the changed bus/device settings the scanner has 
> after reset of server or replugging.
>
> My hope was to have a persistent device-name, which always links to 
> the actual dynamical bus/device number. Therefore the udev-Rule.
>
> The udev-rule works, but the windows clients aren't able to make use 
> of that nor is genesys backend able to work with a symlink.
> I assume that is because genesys (which makes use of libusb) is the 
> bridge to usb, but handles the devices by itself.
>
> That's where I am stuck right now.
>
>
Ah, I think I see. The problem isn't fundamentally a Windows issue. You 
are looking for persistent device naming.
In general, this isn't something that can always be achieved because you 
need something uniquely identifiable to the device.
IIRC the pixma backend manages to do this because pixma devices have a 
serial number that can be queried from the device and this is used to 
build the device name.

Honestly I don't know if genesys devices have this capability, but at 
the moment, devices are identified by the bus location assigned by the 
USB subsystem, which as you say is dynamic.
In your particular case, it *might* be possible to do what you need if 
there is only one device on the Thinkpad machine since you wouldn't care 
which device was selected as there is only one.

I will put some thought into this problem.

Cheers,
Ralph

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://alioth-lists.debian.net/pipermail/sane-devel/attachments/20210806/c54fdde9/attachment.htm>