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

From: Takashi Iwai
Date: Fri Apr 20 2018 - 08:11:03 EST

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)
> }
> }

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

> +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.