Why drm-mipi-dsi is built-in only?

[Thierry Reding]

On Tue, Aug 02, 2016 at 12:47:06PM +0200, Andrzej Hajda wrote:
> On 08/02/2016 10:36 AM, Thierry Reding wrote:
> > On Mon, Aug 01, 2016 at 08:04:55PM +0200, Andrzej Hajda wrote:
> >> On 08/01/2016 03:59 PM, Jani Nikula wrote:
> >>> Cc Andrzej, Thierry
> >>>
> >>> On Fri, 22 Jul 2016, Daniel Vetter <daniel at ffwll.ch> wrote:
> >>>> On Fri, Jul 22, 2016 at 04:30:24PM +0200, Takashi Iwai wrote:
> >>>>> Hi,
> >>>>>
> >>>>> is there any reason drm-mipi-dsi can't be a module?  It's fixed as a
> >>>>> built-in since its Kconfig is bool.
> >>>> Probably none except embedded folks eshew modules ;-) Submit patch, I'll
> >>>> apply.
> >>> Possibly this?
> >>>
> >>> postcore_initcall(mipi_dsi_bus_init);
> >> If I remember correctly, the only reason for this is to have mipi_dsi bus
> >> registered before mipi_dsi drivers, which usually are registered
> >> at module initcall. But maybe bus registration can be performed at
> >> first mipi_dsi driver registration. This way we could modularize it.
> > I think it should work fine if this was built as a module. The purpose
> > for having this as postcore_initcall() is simply so that the bus is
> > fully initialized before any driver gets registered with it. If this
> > code is built as a module, symbol dependencies will make sure that the
> > drm_mipi_dsi.ko module will be loaded before any users.
> 
> If you change initcall of mipi_dsi to module and then you compile
> it as built-in, only link order will guard correct initialization sequence.
> As for now panels are linked after mipi-dsi, so it should be OK,
> even if little bit hacky.

I wasn't suggesting that we turn the postcore_initcall() into
module_init(). postcore_initcall() works just fine for modules (it's
automatically replaced by a module_init() if the code is built as a
module) and it will still do the right thing with regard to ordering
when built-in.

Thierry
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