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

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Message-Id: <93DC0F40-81A5-49C6-A470-0D1B6AA85725@canonical.com>
Date:   Thu, 12 Apr 2018 22:15:41 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Takashi Iwai <tiwai@...e.de>, Lukas Wunner <lukas@...ner.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

at 6:59 PM, Pali Rohár <pali.rohar@...il.com> wrote:

> On Thursday 12 April 2018 12:50:02 Takashi Iwai wrote:
>>> +#if IS_ENABLED(CONFIG_DELL_LAPTOP)
>>> +static bool check_dell_switchable_gfx(struct pci_dev *pdev)
>>> +{
>>> +	bool (*dell_switchable_gfx_is_enabled_func)(void);
>>> +	bool enabled;
>>> +
>>> +	/* Only need to check for Dell laptops and AIOs */
>>> +	if (!dmi_find_device(DMI_DEV_TYPE_OEM_STRING, "Dell System", NULL) ||
>>> +	    !(dmi_match(DMI_CHASSIS_TYPE, "10") ||
>>> +	      dmi_match(DMI_CHASSIS_TYPE, "13")) ||
>>> +	    !(pdev->vendor == PCI_VENDOR_ID_ATI ||
>>> +	      pdev->vendor == PCI_VENDOR_ID_NVIDIA))
>>> +		return false;
> ...
>>> @@ -1711,6 +1745,11 @@ static int azx_create(struct snd_card *card,  
>>> struct pci_dev *pci,
>>>  	if (err < 0)
>>>  		return err;
>>>
>>> +	if (check_dell_switchable_gfx(pci)) {
>>> +		pci_disable_device(pci);
>
> Hi!
>
> Now looking at it again... This code disables all ATI and NVIDIA sound
> cards available in any Dell System (laptop or AIO) if system says that
> SG is enabled, right?

Yes.

>
> It means that also any external ATI or NVIDIA PCI card with audio device
> connected to Thunderbolt (e.g. via PCI <--> TB bridge) is always
> unconditionally disabled too?

I never thought of this case, thanks for bringing this up.
Do you have any suggestion to check if it connects to the system via  
Thunderbolt?

Kai-Heng

>
>>> +		return -ENODEV;
>>> +	}
>
> -- 
> Pali Rohár
> pali.rohar@...il.com