On Fri, Jul 29, 2016 at 09:45:55AM +0200, Hans Verkuil wrote:

> My main problem is not so much with deferred probe (esp. for cyclic dependencies
> it is a simple method of solving this, and simple is good). My main problem is
> that you can't tell the system that driver A needs to be probed after drivers B,
> C and D are probed first.

> That would allow us to get rid of v4l2-async.c which is a horrible hack.
> 
> That code allows a bridge driver to wait until all dependent drivers are probed.
> This really should be core functionality.

> Do other subsystems do something similar like drivers/media/v4l2-core/v4l2-async.c?
> Does anyone know?

ASoC does, it has an explicit card driver to join things together and
that just defers probe until everything it needs is present.  This was
originally open coded in ASoC but once deferred probe was implemented we
converted to that.