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:   Mon, 23 Apr 2018 16:04:55 +0800
From:   Kai Heng Feng <kai.heng.feng@...onical.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     mjg59@...f.ucam.org,
        Pali Rohár <pali.rohar@...il.com>,
        dvhart@...radead.org, andy@...radead.org,
        Mario Limonciello <mario.limonciello@...l.com>, tiwai@...e.com,
        alsa-devel@...a-project.org,
        Linux Kernel Mailing List <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 Apr 20, 2018, at 8:10 PM, Takashi Iwai <tiwai@...e.de> wrote:
>
> 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?

Well, I should say "it hangs the userspace process" instead.

$ speaker-test -t wav -c 2 -D hw:CARD=HDMI,DEV=3
...and it just stopped. Can't Ctrl+C to break it.

>
>
>> @@ -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.

Thanks, will update in next version.

>
>> +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.

Makes sense. Will also update this one.

Kai-Heng

>
>
> thanks,
>
> Takashi