[sane-devel] Using scanimage's -device option to specify one of two identical scanners

[Joel Penner]

Great clarification, it's very interesting stuff. Thanks a lot. I got
another pi to use with the second 9000f; other combinations of scanners on
a single pi should be more successful.

- Joel


On Sun, Feb 23, 2014 at 5:31 PM, Olaf Meeuwissen
<olaf.meeuwissen at avasys.jp>wrote:

>
> Joel Penner writes:
>
> > With both 9000f scanners connected, it's:
> >
> > pi at raspberrypi ~/sambashare2 $ sudo LD_LIBRARY_PATH=/usr/lib/:/lib
> > scanimage -L
> > device `pixma:04A91908' is a CANON Canoscan 9000F multi-function
> peripheral
> > device `pixma:04A91908' is a CANON Canoscan 9000F multi-function
> peripheral
> > pi at raspberrypi ~/sambashare2 $
>
> The "pixma:04A91908" bit is what you pass to scanimage's --device-name
> option.  This is then used by the pixma backend to decide which device
> it should use.  Unfortunately, this backend is not (yet) able to tell
> the two devices apart.
>
> >> On Sun, Feb 23, 2014 at 12:15 AM, Joel Penner <joelcpenner at gmail.com>
> >> wrote:
> >> > Using lsusb -t I get this feedback:
> >> >
> >> > pi at raspberrypi ~ $ lsusb -t
> >> > /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
> >> >     |__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/3p, 480M
> >> >         |__ Port 1: Dev 3, If 0, Class=vend., Driver=smsc95xx, 480M
> >> >         |__ Port 3: Dev 11, If 0, Class=vend., Driver=usbfs, 480M
>
> So the USB layer has no problems telling your two devices apart.  One
> reason that many backends do not want to expose the Dev part of this
> output is that it changes every time you reconnect or power-cycle your
> scanner.  That leads to changing device names, something that confuses
> many users.  The pixma backend is one of those backends and it has opted
> to exposo a device name that does *not* changes across reconnections,
> power-cycling and system reboots.  It does so at the expense of not
> supporting two or more devices of the same make.
>
> >> > I do notice how sane-find-scanner returns the bus/port data:
> >> >
> >> > sudo sane-find-scanner
> >> > found USB scanner (vendor=0x04a9 [Canon], product=0x1908 [CanoScan])
> at
> >> > libusb:001:011
> >> > found USB scanner (vendor=0x0424, product=0xec00) at libusb:001:003
> >> >
> >> > How would I use the libusb:001:011 identifier for the 9000f with
> >> > scanimage?
>
> This would require changes to the pixma backend code.  It could for
> example add support for "pixma:libusb:001:011" style device name,
> possibly as aliases for "pixma:04A91908".  That way, user with only one
> device don't have to bother with the changing device names, but users
> like yourself with more than one would be able to pick one or the other
> with the libusb "alias".
>
> The drawback of this is that it would show twice as many device names as
> are connected.
>
> >> > If I try to tell scanimage to use one of those with the -device
> option, I
> >> > get this feedback:
> >> >
> >> > pi at raspberrypi ~/sambashare $ sudo LD_LIBRARY_PATH=/usr/lib/:/lib
> >> scanimage
> >> > --progress --verbose --batch --format=tiff --resolution=2400 -x 240 -y
> >> 135
> >> > -d libusb:001:011 --batch-start=110000 >
> /home/pi/sambashare/myco%5d.tif
> >> > scanimage: open of device libusb:001:011 failed: Invalid argument
>
> This tells scanimage to look for a libusb SANE backend.  Such a backend
> does not exist so you get the invalid argument error.
>
> Hope this clarifies,
> --
> Olaf Meeuwissen, LPIC-2           FLOSS Engineer -- AVASYS CORPORATION
> FSF Associate Member #1962               Help support software freedom
>                  http://www.fsf.org/jf?referrer=1962
>
> --
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