linux-kernel - RE: [PATCH 5/6] PCI: acpiphp: look _RMV method a bit deeper in the hierarhcy

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Date:	Tue,  2 Jul 2013 13:44:06 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Yinghai Lu <yinghai@...nel.org>, john.ronciak@...el.com,
	miles.j.penner@...el.com, bruce.w.allan@...el.com,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	x86@...nel.org
Subject: RE: [PATCH 5/6] PCI: acpiphp: look _RMV method a bit deeper in the
 hierarhcy

Mika Westerberg wrote:
> The acpiphp driver finds out whether the device is hotpluggable by checking
> whether it has _RMV method behind it (and if it returns 1). However, at
> least Acer Aspire S5 with Thunderbolt host router has this method placed
> behind device called EPUP (endpoint upstream port?) and not directly behind
> the root port as can be seen from the ASL code below:
> 
> Device (RP05)
> {
> 	...
> 	Device (HRUP)
> 	{
> 		Name (_ADR, Zero)
> 		Name (_PRW, Package (0x02)
> 		{
> 			0x09,
> 			0x04
> 		})
> 		Device (HRDN)
> 		{
> 			Name (_ADR, 0x00040000)
> 			Name (_PRW, Package (0x02)
> 			{
> 				0x09,
> 				0x04
> 			})
> 			Device (EPUP)
> 			{
> 				Name (_ADR, Zero)
> 				Method (_RMV, 0, NotSerialized)
> 				{
> 					Return (One)
> 				}
> 			}
> 		}
> 	}
> 
> If we want to support such machines we must look for the _RMV method a bit
> deeper in the hierarchy. Fix this by changing pcihp_is_ejectable() to check
> few more devices down from the root port.

We found that this approach is broken. We've got false positive: host
bridge itself was detected as hotplugable slot %) I think it's not
acceptable.

Mika has tried few more approaches, but we haven't found anything better
then hardcoded path like in original workaround patch[1]. It's not generic
at all, but safe from false positives.

Any thoughts?

[1] http://article.gmane.org/gmane.linux.kernel.pci/19102

-- 
 Kirill A. Shutemov
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