Hi, On Sun, Sep 01, 2002 at 03:07:13PM -0400, Matto Marjanovic wrote: > > >* 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.
Ok, I have added that to the TODO list. Looks like we can make a minor change of the standard now. We shouldn't forget to forward-port that to the 2.0-draft. > 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? sane_set_io_mode must be used after sane_start (and before sane_cancel). > 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". Oh, you can :-) What I do in the Mustek backend in sane_set_io_mode is: if (fcntl (s->pipe, F_SETFL, non_blocking ? O_NONBLOCK : 0) < 0) [...] So that should work even after sane_read. However, if the backend does buffering it may be more difficult. > It certainly doesn't make sense to call sane_set_io_mode() after > sane_read()! I have never tried what happens in that case... > (Maybe this has been gone-over before; I've been on another planet for the > last year....) I don't remember anyone talking about that. Bye, Henning
