[sane-standard] "basic" scanning with usb canoscan?

[Laurent Cocea]

Hello all,

I am aware the Canoscan D646U scanner is not supported as such and would
like to understand whether it is possible to do some basic scanning with
it in xsane or not.

I have two USB devices connected to my RedHat 9 Linux box: a Logitech
Quickcam Web and the Canoscan D646U; they both work fine in Windows on
the same machine. The scanner is correctly detected by the kernel and
the scanner module is loaded, as shown below:

$ dmesg | grep scanner
usb.c: registered new driver usbscanner
scanner.c: USB scanner device (0x04a9/0x220b) now attached to scanner0
scanner.c: 0.4.12:USB Scanner Driver
scanner.c: probe_scanner: User specified USB scanner -- Vendor:Product -
4a9:220b

The Quickcam was initially not detected, so I compiled and installed a
driver from sourceforge.net and now it is correctly detected, as shown
below:

$ dmesg | grep cam
usb.c: registered new driver quickcam
quickcam: QuickCam USB camera found (driver version QuickCam USB $Date:
2004/07/29 18:12:39 $)
quickcam: Kernel:2.4.20-31.9 bus:1 class:FF subclass:FF vendor:046D
product:0850
quickcam: Sensor VV6410 detected
quickcam: Registered device: /dev/video0

So both USB devices are now corectly detected and the drivers (modules)
are loaded at boot time:

$ lsmod
Module                  Size  Used by    Not tainted
scanner                11512   0 (unused)
quickcam               67232   0
videodev                7776   1 [quickcam]
usbcore                73280   1 [scanner quickcam hid usb-ohci]
(...)

I can successfully used the Quickcam with software such as Camorama.
However, I cannot use the Canoscan with xsane.

My questions at this point are:

[1] Why is it necessary to develop another driver (sane-backend) for the
Canoscan D646U USB scanner to work with xsane if the scanner has already
been detected by the kernel and the scanner module has been loaded? A
similar step doesn't seem to be required for the USB webcam to work with
Camorama.   

[2] Is the scanner module loaded by the kernel sufficient for some
"basic" scanning to be carried out in xsane with the Canoscan D646U? If
it is, then how should I configure the sane-backend for this to work?
xsane only detects my webcam; before compiling the Quickcam driver,
xsane could detect no device.

Any help would be greatly appreciated.

--Laurent