linux-kernel - Re: [PATCH v3 3/3] ALSA: hda: Disabled unused audio controller for Dell platforms with Switchable Graphics

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Date:   Sat, 14 Apr 2018 13:17:11 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Takashi Iwai <tiwai@...e.de>, mario.limonciello@...l.com,
        andy@...radead.org, dvhart@...radead.org, mjg59@...f.ucam.org,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v3 3/3] ALSA: hda: Disabled unused audio controller for
 Dell platforms with Switchable Graphics

On Sat, Apr 14, 2018 at 12:49:50PM +0200, Pali Rohár wrote:
> On Saturday 14 April 2018 12:45:12 Lukas Wunner wrote:
> > On Thu, Apr 12, 2018 at 10:15:41PM +0800, Kai-Heng Feng wrote:
> > > Do you have any suggestion to check if it connects to the system via
> > > Thunderbolt?
> > 
> > Just use pci_is_thunderbolt_attached(), introduced by 8531e283bee6,
> > like this:
> > 
> > if (check_dell_switchable_gfx(pci) && !pci_is_thunderbolt_attached(pci))
> 
> And what about PCI-e device attached to ExpressCard slot?

I don't know of a bullet-proof way to recognize those.  In theory
one could check if the PCIe port above the GPU is a non-hotplug
root port, but I think there are machines with hotplug capable
root ports with GPUs below them that aren't actually removable.

However I think ExpressCard-attached GPUs were rare, much less ones
with integrated HDA controller, so in reality that's probably a
non-issue.

Thanks,

Lukas