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Subject: Re: [alsa-devel] [PATCH v4 3/3] ALSA: hda: Disabled unused audio
 controller for Dell platforms with Switchable Graphics
From:   Kai Heng Feng <kai.heng.feng@canonical.com>
In-Reply-To: <s5hbmeew01d.wl-tiwai@suse.de>
Date:   Mon, 23 Apr 2018 16:04:55 +0800
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        Mario Limonciello <mario.limonciello@dell.com>, tiwai@suse.com,
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        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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 <20180420094432.13133-3-kai.heng.feng@canonical.com>
 <s5hbmeew01d.wl-tiwai@suse.de>
To:     Takashi Iwai <tiwai@suse.de>
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> On Apr 20, 2018, at 8:10 PM, Takashi Iwai <tiwai@suse.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