[sane-devel] Re: canoscan 5500F driver ?

[Henning Meier-Geinitz]

Hi,

On Mon, Apr 12, 2004 at 05:08:27PM +0200, Thibault North wrote:
> ok let's go for a test. But I'am beginning, don't go to quickly :)

Ok. First: reply to the sane-devel mailing list, not to me personally :-)

> You are talking of check-usb-chip.c in sane-backend 1.4pre tools directory ?

Yes. It's part of sane-find-scanner. It's used by sane-find-scanner to
find out which kind of USB chip is used. The code tries one chip after
the other. It first tests for the characteristics of the USB device
descriptor and interface descriptors (e.g. USB version, number of
endpoints). If it finds out that the current USB version is 1.1 but
the vhipset has usually 2.0 it's not that chip so the next test is
executed. If all the descriptor characteristics are found to be met, a
short command is sent to the scanner, e.g. to write to a register and
read that value from it again. If that's also ok, the chip is detected
for sure.

> What do I have to do with it ? how to add a test ?

Read the source code. You'll see tests for different chipsets. At the
end of the code, all the different tests are executed one after the
other. Add one test as mentioned in my previous mail.

Check at which test it fails and have a look at the output of
sane-find-scanner -v -v. That output contains all the fields the USB
provides.

> Maybe I should read the documentation first... I'll print it now, 
> perhaps I'll undestand it :)

Have a look at the USB specification. It explains what all these
descriptors are and what the balues mean.

> Programming: i didn't go far, but I will be pleased to learn more... (I 
> did a little of C++, but I don't know C structures at all...)

You'll learn to use them. But in this case, you can just copy the
already existing tests and change the values.

Bye,
  Henning