[sane-devel] Invalid argument (status 4) when calling sane_start

[Gerard Klaver]

On Sun, 2007-12-16 at 10:32 +0100, Peter Gebauer wrote:
> Hi!
> 
> > The v4l backend supports only a few modes so you have to select the correct ones to get a image.
> 
> So it's the v4l settings that are wrong or the SANE settings?
> 
> There's a couple of things I'd fix with the v4l backend
> 
> 1) Default (startup) mode must be valid and supported so a user can 
> sane_start() with the default settings. It makes no sense to put the device 
> in "broken mode" at startup.
> 
> 2) Unsupported modes should not be listed. Why whould you even list 
> options/modes that aren't supported by the backend? Nobody wants a 
> SANE_STATUS_INVAL so nobody will set an unsupported mode anyway. Any modes 
> not supported should be removed from the options.
> 
> If your sane_control_option didn't give an error then that mode should be 
> considered valid and usable setting. This will remove the unwanted surprise 
> when calling sane_start() and it will remove the guess work trying to figure 
> out what option is breaking the sane_start() call.
> 
> I'll look at the v4l backend, but fixing it to work properly would be a 
> major detour from my project. The idea of allowing SANE to use v4l devices 
> is great, it feels generic and... cool. :)
> 
> /Peter
> 
> 

The v4l backend doesn't support all v4l modes.
See also SANE bugreports for some update information (30015,30016,30018)

-- 
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m.vr.gr.
Gerard Klaver