linuxaudio.org

On Fri, 2012-06-01 at 22:56 +0000, Fons Adriaensen wrote:

quoted text
> On Fri, Jun 01, 2012 at 06:42:01PM -0400, David Robillard wrote:

> > On Fri, 2012-06-01 at 22:22 +0000, Fons Adriaensen wrote:

> > > On Fri, Jun 01, 2012 at 06:09:06PM -0400, David Robillard wrote:

> > >

> > > > LV2_Buf_Size_Status

> > > > get_block_length(LV2_Buf_Size_Buf_Feature_Handle handle,

> > > >                  uint32_t*                       min,

> > > >                  uint32_t*                       max,

> > > >                  uint32_t*                       multiple_of,

> > > >                  uint32_t*                       power_of);

> > > >

> > >

> > >

> > > > This callback just describes reality to the plugin at instantiation

> > > > time.

> > >

> > > That 'to the plugin' confuses me - isn't this supposed to be

> > > the plugin telling the host what it (the plugin) needs ?

> >

> > This is a host-provided callback which the plugin can use at

> > instantiation time to figure out the block length characteristics,

> > whatever they may be.

>

> (Maybe it's just too late for me to grok this...)

>

> So it's the plugin asking the host what it can expect ?

Yes.
> Isn't the LV2 way to do this via features (i.e. the plugin

quoted text
> checking which features the host provides) ?

Yes, this callback is in a feature struct.  Essentially "feature" just

means "thing provided by the host"[1].
Restrictions would also be features, but nevermind that.  Regardless of

restrictions, plugins need to know the actual situation (for example,

right now I need to know max, and have no restrictions).  It decomposes

nicely.
Not mentioning any of that was no mistake[2]; I am attempting to farm

precisely one piece of information: whether or not the above callback

can adequately express any reasonable block length situation; i.e.

whether or not any plugin could know "yes, I can run" or "no, my

requirements to run are not met".
There is no point confusing the thread with restrictions since that part

follows directly from the above.
Also, I said something stupid about constant size earlier.  Of course,

constant can be expressed with min == max.
-dr
[1] Poor choice in terminology here, it turns out
[2] I know this stupid list and how to extract useful information from

it and ignore the rest ;)
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