[FFmpeg-devel] [PATCH] Return ENOTSUP if codec does not support feature

[Michael Niedermayer]

Hi

On Fri, Jul 20, 2007 at 12:24:40PM -0400, Ronald S. Bultje wrote:
> Hi,
> 
> On 7/20/07, Panagiotis Issaris <takis.issaris at uhasselt.be> wrote:
> >
> > Do you know a source for the correct and exact meaning of these
> > codes? I am only aware of the OpenGroup's website, but the
> > definitions on that site aren't really clear:
> > [ENOTSUP] Not supported.
> > [ENOSYS] Function not supported.
> > [EINVAL] Invalid argument.
> > ...
> >
> > As can be found here:
> > http://www.opengroup.org/onlinepubs/009695399/basedefs/errno.h.html
> 
> 
> The best descriptions are in the man pages, but they are syscall-specific.
> There is no general, good resource, I'm affraid.
> 
> If you were referring to the definition in the libc infopages, I'd
> > interpreted them differently. It says (notice the empasis I added):
> > "... the functionality they request is not available. This _can_ mean
> > that the function does not implement a particular command ..."
> >
> > I had read that as, "the codec does not provide that functionality",
> > not meaning the implementation, but that the feature can't be used
> > for a codec. And that a complete implementation of the codec would
> > not have provided it either.
> 
> 
> Either way, this is just as ambiguous as the "not supported" vs. "invalid
> parameter". :-). It can be read either way. One way to solve it is to just
> do the same that syscalls do - pick a few, extend and specify their meaning
> more clearly in a document and use those in that exact way.

yes, clearly specifying the meaning would be a good idea
suggestion below:

ENOTSUP
    What you want me to do is possible (within the limits of the standards
    unless you asked that i violate them) but i dont support it, though
    you could patch me so i do support that.

EINVAL
    Some arguments or their combination is invalid

ENOSYS
    What you want me to do is possible (within the limits of the standards
    unless you asked that i violate them) but i was not compiled with support
    for it.



[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
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