Re: [RFC] compress: add support for gapless playback

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

>>>> +	if (!stream->ops->set_metadata)
>>>> +		return -ENXIO;
>
>>> Is this really a fatal error? Or do we want to mandate that gapless
>>> be supported by all implementations?
>
>> Fatal err? if DSP doesnt support metadata callback then we are reporting error
>> ENXIO to userpsace. No we shouldnt mandate, its upto DSP folks to see what they
>> should and can support.
>
> Well, up to userspace to see how it handles the error anyway.  For
> example an application may want to fall back to PCM playback with
> gapless done on the CPU if the driver doesn't do it.  But then given
> that there's more than one piece of metadata in the struct perhaps we
> need some way for the application to figure out what's supported?

Maybe we should expose what's supported as part of the decoder query 
process, i.e. expose support for metadata as part of the decoder 
capabilities rather than as part of the set_metadata part? Error checks 
after inits are painful. we could have a "metadata_support" bit-field 
that the application could check.