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Message-ID: <b115cb5f05072903233fef8dc3@mail.gmail.com>
Date: Fri, 29 Jul 2005 19:23:40 +0900
From: Rajat Jain <rajat.noida.india@gmail.com>
Reply-To: Rajat Jain <rajat.noida.india@gmail.com>
To: Rajesh Shah <rajesh.shah@intel.com>
Subject: Re: Re: Problem while inserting pciehp (PCI Express Hot-plug) driver
Cc: Kristen Accardi <kristen.kml@gmail.com>, greg@kroah.com,
       linux-kernel@vger.kernel.org, linux-newbie@vger.kernel.org,
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On 7/29/05, Rajesh Shah <rajesh.shah@intel.com> wrote:
> On Thu, Jul 28, 2005 at 07:45:49PM +0900, Rajat Jain wrote:
> >
> > Okay. I'm sorry but I'm not very clear with this. I'm just putting
> > down here my understanding. So basically we have two mutually
> > EXCLUSIVE hotplug drivers I can use for PCI Express:
> >
> A hotplug slot can be controlled only by a single hotplug
> technology - pcie shpc or acpiphp. However, different parts of
> the I/O hierarchy can be controlled by different technologies.
> For example, a host bridge I/O complex can be hotplugged using
> acpiphp, but end devices under this IO complex may be hotpplugged
> using pcie or shpc hotplug.
> 
> > 1) "pciehp.ko" : We use this PCIE HP driver when our BIOS supports
> > Native Hot-plug for PCI Express (which means that hot-plug will be
> > handled by OS single handedly).
> >
> > 2) "acpiphp.ko" : We use this "generic" ACPI HP driver when BIOS
> > allows only ITSELF to handle hot-plug events.
> >
> No, acpi hotplug is not handled by BIOS only.
> Both acpi and pcie hotplug need firmware support as well as hardware
> support. Hardware in many (but not all) systems support both types of
> hotplug and its up to the BIOS to decide which type to support. If the
> platform supports pcie hotplug, you see an _OSC & _SUN methods in the
> ACPI namespace and the pciehp driver controls hotplug slots. If the
> system supports acpi hotplug, you see _ADR and _EJ0 methods in the ACPI
> namespace and the acpiphp driver controls the corresponding hotplug slots.
> 
> Rajesh
> 

Thanks a lot. It has proved to be a very useful information for me. I
can now do some R&D on it.

Thanks again,

Rajat