[sane-devel] platform independent sanei_usb control messages
Sun, 30 Jun 2002 18:28:00 +0200
On Sun, Jun 30, 2002 at 03:36:35PM +0200, Bertrik Sikken wrote:
> I'm working on a backend for scanners based on the 'niash' chipset,
> found in scanners like
> the HP3300, HP3400, HP4300, (HP5400?) and the Agfa Snapscan Touch.
> Until now I've used libusb to provide platform independent USB access
> which works
> mostly fine. I know there's also the sanei_usb functions, but I have
> some issues using them.
I'm currently working on making sanei_usb more generic. That means,
sanei_usb should also be able to use libusb, not only the
"Linux-kernel-method" (which works with the BSDs, also).
It's not yet finished and there may be problems but I think I will add
a first version to CVS during the next few days.
The idea is that no changes in the backends are necessary.
> When I do a control transfer I need to pass some parameters involving
> (for example)
> USB_TYPE_VENDOR, USB_RECIP_DEVICE and USB_DIR_IN which
> are defined in linux/usb.h, obviously not platform independent.
Yes, usually it's better to copy the needed constants.
> I see that the canon630u backend solved this by defining those symbols
> I suspect that the symbols mentioned above are really part of the USB
I thinks o, but I will have a closer look when implementing
sanei_usb_control_msg for libusb.
> so they are not platform specific. Maybe it's a good idea to add them to
Yes. Proposals for what to include are welcome :-)
> What is actually the preferred USB access method for SANE?
Depends on who you ask. My personal opinion is: kernel access via
scanner module. Most sane backends currently use sanei_usb or direct
access to /dev/usb/scanner*.
> And for what reasons?
+ is portable for different platforms (OS X?)
+ automatic detection of scanners is easier
- need to be root to access devices
- no way to scan for scanners in sane-find-scanner
the other way round :-)
That's why I try to include libusb access in sanei_usb to get best of
both worlds. Maybe other (proprietary) access methods (e.g. for
Solaris?) can be added too, once the file is more generic.