[LV2] --SPAM--::Re: [Devel] lv2_descriptor() considered harmful

[David Robillard]

On Mon, 2012-02-27 at 00:48 +0100, Stefan Kersten wrote:
> On 26.02.12 23:08, David Robillard wrote:
> > On Sun, 2012-02-26 at 14:28 +0100, Stefan Kersten wrote:
> > [...]
> >> my use case is an extension that allows realtime-safe instantiation (and
> >> destruction) of plugins. currently the interface to be provided by the plugin
> >> via extension_data looks like this:
> >>
> >> typedef struct
> >> {
> >>     void (*initialize)(LV2_Descriptor *                   descriptor,
> >>                        const char *                       bundle_path,
> >>                        const LV2_Feature *const *         features);
> >>     void (*release)(LV2_Descriptor *                      descriptor);
> >>
> >>     uint32_t (*instance_size)(const LV2_Descriptor *      descriptor);
> >>     uint32_t (*instance_alignment)(const LV2_Descriptor * descriptor);
> >>
> >>     LV2_Handle (*instantiate)(const LV2_Descriptor *      descriptor,
> >>                               void *                      location,
> >>                               double                      sample_rate);
> >> } LV2_RT_Instantiate_Interface;
> >>
> >> the main point here is that the host's feature set is required during library
> >> (or descriptor) initialization, because potentially non-realtime-safe calls
> >> (e.g. to the urid extension) cannot be made from within instantiate and their
> >> results need to be cached beforehand.
> > 
> > Wouldn't it be simpler/better to just have the host pass an allocator?
> 
> the idea is to keep instance creation overhead as low as possible; "placement"
> instantiation saves one call to the allocator and is possible for many plugins
> (in my case most of them generated by faust). an allocator feature still makes
> sense though, for plugins that don't know their memory requirements at compile time.

Fair enough (though it's just one function call).  What do you need
dynamic alignment for?

> > Presumably initialize and release would go away if the new discovery API
> > was there to use.
> 
> yes. i've been rolling my own plugin API when i realized that LV2 does almost
> everything i need and is extensible enough to make it do virtually anything.
> good work!

Best to get along with others if at all possible :)

Thanks,

-dr