linux-kernel - Re: [PATCH] pciehp: Add pciehp

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Message-ID: <s5hppytq430.wl%tiwai@suse.de>
Date:	Wed, 20 Mar 2013 20:11:15 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Oliver Neukum <oneukum@...e.de>, Michal Marek <mmarek@...e.cz>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pciehp: Add pciehp_surprise module option

At Wed, 20 Mar 2013 17:52:34 +0000,
Matthew Garrett wrote:
> 
> On Wed, Mar 20, 2013 at 03:02:01PM +0100, Takashi Iwai wrote:
> > We encountered a problem that on some HP machines the Realtek PCI-e
> > card reader device appears only when you inserted a card before the
> > cold boot.  While debugging, it turned out that the device is actually
> > handled via PCI-e hotplug in some level.  The device sends a presence
> > change notification, and pciehp receives it, but it's ignored because
> > of lack of the hotplug surprise (PCI_EXP_SLTCAP_HPS) capability bit.
> > Once when this check passes, everything starts working -- the device
> > appears upon plugging the card properly.
> 
> Well that just sounds like a bug. What's the downside to just ignoring 
> that capability bit?

I'm afraid that it's too radical to enable always.
Or, what about to check this bit only for disable path?
Enabling the device is usually not to worry much.  The problematic
part is rather the surprising device disablement.

Just my $0.02.


thanks,

Takashi
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