On Thu, Dec 13, 2012 at 10:44:41AM -0800, Greg KH wrote:

On Thu, Dec 13, 2012 at 05:31:46PM +0200, Kirill A. Shutemov wrote:

quoted

From: "Kirill A. Shutemov" <redacted>

Correct ACPI PCI hotplug imeplementation should have _RMV method in a
PCI slot (device under pci bridge). In Acer Aspire S5 case we have it
deeper in hierarchy:

Device (RP05)
{
   // ...
   Device (HRUP)
   {
       // ...
       Device (HRDN)
       {
           // ...
           Device (EPUP)
           {
               // ...
               Method (_RMV, 0, NotSerialized)  // _RMV: Removal Status
               {
                   Return (One)
               }
           }
       }
   }
}

Signed-off-by: Kirill A. Shutemov <redacted>
---
 drivers/pci/hotplug/acpi_pcihp.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/pci/hotplug/acpi_pcihp.c b/drivers/pci/hotplug/acpi_pcihp.c
index 2a47e82..d92ebfb 100644
--- a/drivers/pci/hotplug/acpi_pcihp.c
+++ b/drivers/pci/hotplug/acpi_pcihp.c

@@ -422,6 +422,19 @@ static int pcihp_is_ejectable(acpi_handle handle)
 	status = acpi_evaluate_integer(handle, "_RMV", NULL, &removable);
 	if (ACPI_SUCCESS(status) && removable)
 		return 1;
+
+	/*
+	 * Workaround for Thunderbolt implementation on Acer Aspire S5.
+	 *
+	 * Correct ACPI PCI hotplug imeplementation has _RMV method in a PCI
+	 * slot (device under pci bridge). In Acer Aspire S5 case we have it
+	 * deeper in hierarchy.
+	 */
+	status = acpi_evaluate_integer(handle, "HRDN.EPUP._RMV", NULL,
+			&removable);
+	if (ACPI_SUCCESS(status) && removable)
+		return 1;

I have no objection to this patch as-is, but I wonder how will other
BIOSes implement this "incorrectly" in the future.  Should we always
just try to walk the whole PCI slot heirachy looking for the _RMV
attribute?  That should solve the problem where someone else places this
at another location for the slot, right?

I'm new with PCI and I'm not sure what problems can cause false positive
here.
What will heppend if we find yet another PCI-to-PCI bridge in the hierarchy
and some of slots of that bridge will have _RMV method? Is it possible,
right?

I prefer postpone any generalization before we will find any similar bug
on other HW. (I naively hope BIOS developers will not repeat theirs bugs).

Is there any test for Windows that ensures that this gets placed in the
"correct" location that we can rely on?

No idea. I haven't seen any Windows.

-- 
 Kirill A. Shutemov