Re: [RFC PATCH 1/2] ACPI / PNP: Don't add "enumeration_by_parent" devices

[John Garry]

On 20/04/2018 14:52, Mika Westerberg wrote:
> On Fri, Apr 20, 2018 at 02:24:18PM +0100, John Garry wrote:
> > Hi Mika,
> >
> > On 20/04/2018 14:07, Mika Westerberg wrote:
> > > On Fri, Apr 20, 2018 at 06:07:25PM +0800, John Garry wrote:
> > > > +	} else {
> > > > +		device->driver_data = dev;
> > >
> > > I think this deserves a comment explaining why we (ab)use driver_data
> > > like this.
> >
> > Sure, could add. I didn't see any other way for the acpi_device structure to
> > reference the derived PNP device.
> >
> > TBH, This overall approach is not good since we are creating the PNP device
> > in the scan, and then leaving the device in limbo, waiting for the parent to
> > add it, if at all. There's no rule for this.
> >
> > So I'm looking for ideas on how to improve this.

Hi Mika,

> One idea is to make pnpacpi_add_device() available outside of PNP and
> call it directly (or some variation) in hisi_lpc.c when it walks over
> its children.

I did consider this initially and it seems quite straightforward.

However I think the problem is that we would need to modify the 
acpi_device child resources from FW with kernel-specific resources, 
which does not seem right (I think that is what you meant). As I see, 
this is one reason that we went in the direction of modelling the host 
as an MFD, as we could set the resources of the mfd_cells.

So adding a variant of pnpacpi_add_device() could work, or modifying 
pnpacpi_add_device() to accept a callback to translate the resources. 
But this feature is specific to our very special requirement...

Thanks,
John

> .