linux-kernel - Re: [PATCH] ASoC: rt715:add Mic Mute LED control support

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Date:   Tue, 3 Nov 2020 18:31:54 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Limonciello, Mario" <Mario.Limonciello@...l.com>
Cc:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "Yuan, Perry" <Perry.Yuan@...l.com>,
        "oder_chiou@...ltek.com" <oder_chiou@...ltek.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tiwai@...e.com" <tiwai@...e.com>
Subject: Re: [PATCH] ASoC: rt715:add Mic Mute LED control support

On Tue, Nov 03, 2020 at 06:04:49PM +0000, Limonciello, Mario wrote:

> I don't think it came through in the commit message, but I wanted to mention
> in the system that prompted this software does not control the LED.  The LED
> is actually controlled by hardware, but has circuitry to delay the hardware
> mute until software mute is complete to avoid any "popping noises".

Ah, this doesn't correspond to the description at all.

> The flow is:
> User presses mute key, dell-wmi receives event, passes to dell-privacy-wmi.
> This emits to userspace as KEY_MICMUTE.  Userspace processes it and via UCM
> switches get toggled.  The codec driver (or subsystem perhaps) will use LED
> trigger to notify to change LED.  This gets picked up by dell-privacy-acpi.

> dell-privacy-acpi doesn't actually change LED, but notifies that SW mute was
> done.

> If none of that flow was used the LED and mute function still work, but there
> might be the popping noise.

With a timeout so that if things get lost somewhere then the mute button
is still functional, or can userspace block mute?  Also what happens if
userspace tries to set the state without having done anything about
muting, will it trigger the hardware level mute as though the key had
been pressed?

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