[Intel-gfx] [RFC] i915: make the probe asynchronous

[Feng Tang]

On Mon, Jun 25, 2018 at 05:36:32PM +0200, Daniel Vetter wrote:
 > 
> > The binding with i915 from HD-audio controller is done in an async
> > work invoked from the probe callback.  It makes harder to deal with
> > EPROBEDEFER.
> > 
> > IMO, a saner way would be to rather wait for the component binding.
> > The component mechanism is there just for that purpose, after all.
> > 
> > Does a patch like below work (totally untested)?
> 
> Yeah this looks like a reasonable first step at least. Probably need to
> thread the real errno value through, and at that point probably better to
> just nuke the async worker (and maybe switch all of hda over to async
> driver loading instead).
> -Daniel

Hi Daneil/Jani/Takashi,

When I was testing this patch from Takashi, I further checked the kernel
module code, and found that: we may need NOT to add any new codes to
prepare for i915's async probe feature!

Say when i915 module is being loader due to HDA's request_module() call,
in the callchain, do_init_module() has such code:

    if (!mod->async_probe_requested && (current->flags & PF_USED_ASYNC))
                async_synchronize_full();

This will garantee the asynced probe is done before it returns.

I have just tested and this seems to be enough. If I am not wrong, then
we can take the i915 async patch directly. What do you think?

Thanks,
Feng