linux-kernel - Re: [PATCH v2 6/8] PCI: acpiphp: workaround for Thunderbolt on Acer Aspire S5

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Date:	Fri, 19 Jul 2013 14:18:41 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	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,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 6/8] PCI: acpiphp: workaround for Thunderbolt on Acer Aspire S5

On Thursday, July 18, 2013 09:57:23 PM Robert Hancock wrote:
> On 07/03/2013 03:40 PM, Rafael J. Wysocki wrote:
> > On Wednesday, July 03, 2013 05:04:53 PM Mika Westerberg wrote:
> >> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> >>
> >> 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 <kirill.shutemov@...ux.intel.com>
> >> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> >> ---
> >>   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);
> >
> > Well, calling stuff like this directly from a general function is kind of ugly.
> >
> > Can we use something like a quirk instead?  A DMI check or something?
> 
> Presumably this device functions under Windows so clearly Windows is 
> capable of dealing with this case, so we should too.
> 
> There are way too many of these silly DMI checks in the kernel - we 
> should be way more hesitant to add more of them. They're almost 
> guaranteed to be incomplete. I would say they should be avoided whenever 
> possible unless there's some reason why a general workaround can't be used.

This horse is already dead. :-)

Please check the series I posted the day before yesterday.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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