linux-kernel - Re: [alsa-devel] [PATCH v4 3/3] ALSA: hda: Disabled unused audio controller for Dell platforms with Switchable Graphics

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Date:   Fri, 20 Apr 2018 14:10:54 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     mjg59@...f.ucam.org, pali.rohar@...il.com, dvhart@...radead.org,
        andy@...radead.org, mario.limonciello@...l.com, tiwai@...e.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [alsa-devel] [PATCH v4 3/3] ALSA: hda: Disabled unused audio       controller for Dell platforms with Switchable Graphics

On Fri, 20 Apr 2018 11:44:32 +0200,
Kai-Heng Feng wrote:
> 
> Now it's a typical discrete-only system. HDMI audio comes from AMD audio
> controller, others from Intel audio controller.
> 
> When SG is enabled, the unused AMD audio contoller still exposes its
> sysfs, so userspace still opens the control file and stream. If
> userspace tries to output sound through the stream, it hangs the system.

Hm, could you give more information about how it hangs?


> @@ -1627,6 +1629,42 @@ static void check_msi(struct azx *chip)
>  	}
>  }
>  
> +#if IS_ENABLED(CONFIG_DELL_LAPTOP)

This should be IS_REACHABLE(), as both dell-laptop and HD-audio are
tristate.

> +static bool check_dell_switchable_gfx(struct pci_dev *pdev)

I'd remove "_dell" word here.  Such a check would be likely needed for
other vendors, and it's quite possible that the function will be
extended to cover a wider DMI table.


thanks,

Takashi