Re: [PATCH v4 02/10] drm/ingenic: Add support for JZ4780 and HDMI output

[Paul Cercueil]

Hi,

Le mar., sept. 28 2021 at 14:06:03 +0200, H. Nikolaus Schaller 
<hns@xxxxxxxxxxxxx> a écrit :
> Hi Paul,
>
> >  Am 28.09.2021 um 12:21 schrieb H. Nikolaus Schaller 
> > <hns@xxxxxxxxxxxxx>:
> >
> > > >  @@ -1492,10 +1555,16 @@ static int ingenic_drm_init(void)
> > > >  {
> > > >  	int err;
> > > >  +	if (IS_ENABLED(CONFIG_DRM_INGENIC_DW_HDMI)) {
> > > >  +		err = platform_driver_register(ingenic_dw_hdmi_driver_ptr);
> > > >  +		if (err)
> > > >  +			return err;
> > > >  +	}
> > >
> > >  I don't see why you need to register the ingenic-dw-hdmi driver 
> > > here. Just register it in the ingenic-dw-hdmi driver.
> >
> >  Ok, I never though about this (as the code was not from me). We 
> > apparently just followed the IPU code pattern (learning by example).
> >
> >  It indeed looks not necessary and would also avoid the 
> > ingenic_dw_hdmi_driver_ptr dependency.
> >
> >  But: what is ingenic_ipu_driver_ptr then good for?

It's done this way because ingenic-drm-drv.c and ingenic-ipu.c are both 
compiled within the same module ingenic-drm.

I'm not sure this is still required, maybe ingenic-ipu.c can be its own 
module now.

> >  If we can get rid of this as well, we can drop patch 1/10 
> > ("drm/ingenic: Fix drm_init error path if IPU was registered") 
> > completely.
>
> A quick test shows that it *is* required. At least if I configure 
> everything as modules.
> But like you I can't explain why.

Well, a quick test here shows that it is not required, at least when 
configuring with everything built-in.

-Paul

> Well, just a very rough idea (may be wrong): the bridge chain is not 
> like an i2c bus and
> clients are not automatically loaded/probed if linked in the device 
> tree. Therefore the
> consumer (ingenic_drm_drv) must register the "clients" like IPU and 
> HDMI.
>
> BR,
> Nikolaus