[sane-devel] genesys backend

[Pierre Willenbrock]

Hi

The attached patch against experimental cvs leads to a mostly working
Canon LiDE 35. There is support for color and grey scans at arbitrary
resolutions. There are some shortcomings in the code, but those are
mostly structural.

Currently known bugs:
    1 You need to replug the scanner every other retry
    2 Sometimes the calibration process hangs
    3 Some scanning rects lead to stange behaviour
    4 Lineart not supported
    5 No powersaving(after first use draws about 100mA)

5 should be easy, as i already figured out the needed gpios and
registers. But powersaving is rather optional, and other problems are
more pressing.

4 is some work, as a lot of functions need to be made aware of single
bit data.

2 and 3 fall in the category (sometimes) reproducible, but no clue why
these happen. Does anyone have a patch for valgrind to work with libusb?

For 1 i guess i need more documentation on the usb interface of the
scanner. The windows driver does some things(other than register and
bulk transfers) i don't understand, so i didn't implement them in the
backend. If there is any documentation on the usb interface, please
point me to it. The documentation on the chips does not include this.

Next i will implement the slope table generation in the way Stéphane
suggested.

The attached patch needs to be uncompressed with bunzip2. gzip did
compress only to about 50kb.

Regards,
  Pierre
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