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 12:49:50 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Lukas Wunner <lukas@...ner.de>
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 Saturday 14 April 2018 12:45:12 Lukas Wunner wrote:
> On Thu, Apr 12, 2018 at 10:15:41PM +0800, Kai-Heng Feng wrote:
> > > >>@@ -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);
> > > 
> > > 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?
> > > 
> > > 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?
> 
> 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?

> > >>>+	/* 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;
> 
> It sure would be nice if someone could add macros for the chassis type
> to include/linux/dmi.h so that we don't have to use these magic numbers
> everywhere:
> 
> $ git grep -l DMI_CHASSIS_TYPE
> drivers/firmware/dmi-id.c
> drivers/firmware/dmi_scan.c
> drivers/input/keyboard/atkbd.c
> drivers/input/serio/i8042-x86ia64io.h
> drivers/platform/x86/asus-wmi.c
> drivers/platform/x86/dell-laptop.c
> drivers/platform/x86/samsung-laptop.c
> include/linux/mod_devicetable.h
> scripts/mod/file2alias.c
> 
> Thanks,
> 
> Lukas

-- 
Pali Rohár
pali.rohar@...il.com

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