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

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Date:	Thu, 4 Oct 2012 14:47:56 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Len Brown <lenb@...nel.org>,
	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 Thu, Oct 4, 2012 at 2:14 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Thu, Oct 4, 2012 at 12:44 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>>
>> To answer your specific question, yes, I do think drivers that are
>> statically built in probably should be registered before devices are
>> enumerated.  That way, the boot-time case is more similar to the
>> hot-add case.
>>
>> Obviously, for drivers that can be modules, the reverse must work as
>> well (enumerate devices, then load and register the driver).  And then
>> the other order (register driver, then enumerate device) must also
>> work so future hot-adds of the same device type work.
>
> so you will have to handle two paths instead one.

I'm not proposing any additional requirements; I'm just describing the
way Linux driver modules work.  Any module *already* must support both
orders (enumerate devices then register driver, as well as register
driver then enumerate and bind to a hot-added device).  And this
should not be two paths, it should be one and the same path for both
orders.

> current booting path sequence are tested more than hot add path.

True.  You're proposing fiddling with driver binding order so we can
use the current boot path ordering at hot-add time.  I'm suggesting
that the "register driver then enumerate device" order is something we
have to support for hot-add anyway, and that we should use the same
ordering at boot-time.  That's more change for the boot-time path, but
I think it's cleaner and more maintainable in the long term.
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