Re: [Pcihpd-discuss] [PATCH] Fix PCIe hotplug for Dell notebook ExpressCard slots

Kristen Carlson Accardi
2007-10-16T22:52:40Z

On Tue, 16 Oct 2007 15:03:54 -0700
Greg KH <greg@kroah.com> wrote:

> On Tue, Oct 16, 2007 at 05:57:03PM -0400, Mark Lord wrote:
> > Fix PCIe Hotplug so that it works with ExpressCard slots on Dell notebooks
> > in conjunction with modparam of pciehp_force=1.
> >
> > The PCIe Hotplug driver has two shortcomings when used on Dell notebooks
> > which lack ACPI BIOS support for PCIe hotplug:
>
> Wait, Dell explicitly says that pci hotplug of express cards is not
> supported and is broken on these laptops. This is because the version
> of Windows they support on these machines also does not support
> hotplugging these devices.

Just to add to why sometimes vendors disable PCIe hotplug by not providing
_OSC - sometimes there are problems with the hardware itself, and so
due to schedule and other reasons, vendors will decide to just disable
the support by not providing OSC, since really according to spec we shouldn't
be running the PCIe hot plug driver if OSC doesn't exist or fails. This
can be anything from "Well, we don't have time to test it" to actual hardware
errata. At any rate, we don't know the reasons. I think when we force these
things, you run the danger that things will break on you in some strange
ways.

Just out of curiosity, did you try using ACPI based hotplug for this
laptop? Sometimes vendors will let you do that because then they can include
hardware workarounds in the AML.