Re: [PATCH 4/9] PCI: create platform devices for child OF nodes of the port node

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Jan 18, 2024 at 11:58:50AM +0100, Bartosz Golaszewski wrote:
> On Wed, Jan 17, 2024 at 5:45 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Jan 17, 2024 at 05:07:43PM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > >
> > > In order to introduce PCI power-sequencing, we need to create platform
> > > devices for child nodes of the port node.
> >
> > Ick, why a platform device?  What is the parent of this device, a PCI
> > device?  If so, then this can't be a platform device, as that's not what
> > it is, it's something else so make it a device of that type,.
> >
> 
> Greg,
> 
> This is literally what we agreed on at LPC. In fact: during one of the
> hall track discussions I said that you typically NAK any attempts at
> using the platform bus for "fake" devices but you responded that this
> is what the USB on-board HUB does and while it's not pretty, this is
> what we need to do.

Ah, you need to remind me of these things, this changelog was pretty
sparse :)

> Now as for the implementation, the way I see it we have two solutions:
> either we introduce a fake, top-level PCI slot platform device device
> that will reference the PCI host controller by phandle or we will live
> with a secondary, "virtual" platform device for power sequencing that
> is tied to the actual PCI device. The former requires us to add DT
> bindings, add a totally fake DT node representing the "slot" which
> doesn't really exist (and Krzysztof already expressed his negative
> opinion of that) and then have code that will be more complex than it
> needs to be. The latter allows us to not change DT at all (other than
> adding regulators, clocks and GPIOs to already existing WLAN nodes),
> reuse the existing parent-child relationship between the port node and
> the instantiated platform device as well as result in simpler code.
> 
> Given that DT needs to be stable while the underlying C code can
> freely change if we find a better solution, I think that the second
> option is a no-brainer here.

Ok, I remove my objections, sorry about that, my confusion.

greg k-h