linux-kernel - Re: [PATCH 0/4] ACPI: kill acpi_pci_root

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Message-ID: <1391924.CXAbAIeqJX@vostro.rjw.lan>
Date:	Mon, 08 Oct 2012 22:12:11 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Len Brown <lenb@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH 0/4] ACPI: kill acpi_pci_root_start

On Friday 05 of October 2012 16:10:43 Yinghai Lu wrote:
> On Fri, Oct 5, 2012 at 4:01 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > On Thursday 04 of October 2012 15:46:39 Yinghai Lu wrote:
> >> > Your patches seem to affect all devices in the ACPI namespace added after
> >> > boot, though, not only host bridges.
> >>
> >> yes, but it still should be safe.
> >
> > I'm not really sure of that (what about undock/dock, for exmaple?) and it's
> > damn ugly.
> 
> only one acpi_driver has .start , that is acpi_pci_root_driver.
> 
> should be clean than with .add/start pair.
> 
> >
> >> > And the problem seems to be that the scanning of the ACPI namespace and
> >> > configuring the host bridge are kind of independent operations now.  What
> >> > we should do, actually, seems to be something like this:
> >> >
> >> > (1) Configure the host bridge when discovered (i.e. do what the current
> >> >     acpi_pci_root_add() does.
> >> > (2) Parse the ACPI namespace under the host bridge (without binding ACPI
> >> >     drivers to the struct acpi_device objects created in the process,
> >> >     because they are known to correspond to PCI devices).
> >> > (3) Run pci_bus_add_devices() for the bridge.
> >> >
> >> > in one routine.
> >>
> >> problem is still there. if 1 still has acpi_pci_root_add and pci_acpi_scan_root
> >
> > OK, so why don't we do (2) in acpi_pci_root_add(), before pci_acpi_scan_root()
> > is called?
> >
> >> that scan pci devices. what is need is we need to bind 1 and 3 together.
> 
> some one already walk the acpi space, and during that it create
> acpi_device for pci_root
> and then attach driver for that, aka acpi_pci_root_add is executing.
> 
> Now you want to walking the acpi acpi space to create children devices
> before device_add really done for that pci root
> acpi device. ?
> 
> is that some kind of nesting?

Yes, basically.  The idea is to do the scan of the host bridge's children in
the ACPI tree synchronously within acpi_pci_root_add() instead of trying to
delay the execution of it until the children have been scanned (and using
notifiers to kind of trigger the driver binding, i.e. the execution of .add()).

> > I don't understand now.  You said previously that we need the ACPI namespace
> > below the bridge to be scanned before (3), so why do you want to do (3) before
> > (2) now?
> 
> purpose is calling pci_bus_add_devices in pci_acpi_scan_root.

OK, but what's the reason?

Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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