[sane-devel] backend integration

[Matto Marjanovic]

 >* strictly speaking sane_set_io_mode() should return SANE_STATUS_GOOD
 >  for non_blocking == SANE_FALSE, at least that's what the standard
 >  says. I guess nobody will ever notice...

A suggestion for a very tiny edit in the API docs:

   4.3.12 sane_set_io_mode
   ...
   This function may fail with one of the following status codes:

       SANE_STATUS_INVAL:
              No image acquisition is pending. 

       SANE_STATUS_UNSUPPORTED:
---           The backend does not support this operation.
+++           The backend does not support the requested I/O mode.



Hmm... and the more I look at this, the less I understand what the 
 SANE_STATUS_INVAL case is for.  (The microtek backend is blocking-mode
 exclusively, so I've never really dealt with this....)  What does 
 "image acquistion is pending" mean?  Is that before or after sane_start()
 has been called?

It seems to me that the backend would want the frontend to call 
 sane_set_io_mode() *before* sane_start() --- so that sane_start() can
 decide how to set up any data pipes, threads, etc.  And then, after
 sane_start() has been called and the imaging process is under way, 
 sane_set_io_mode() should return SANE_STATUS_INVAL, because "you can't
 change your mind after the scan has begun".  It certainly doesn't make
 sense to call sane_set_io_mode() after sane_read()!

(Maybe this has been gone-over before; I've been on another planet for the
 last year....)
-matt m.