Re: [PATCH v2 01/12] ALSA: doc: Clarify IEC958 controls iface

From: Takashi Iwai <tiwai@suse.de>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Jaroslav Kysela <perex@perex.cz>, Mark Brown <broonie@kernel.org>,
	dri-devel@lists.freedesktop.org,
	Daniel Vetter <daniel.vetter@intel.com>,
	David Airlie <airlied@linux.ie>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Takashi Iwai <tiwai@suse.com>,
	devicetree@vger.kernel.org,
	Dave Stevenson <dave.stevenson@raspberrypi.com>,
	Phil Elwell <phil@raspberrypi.com>,
	Tim Gover <tim.gover@raspberrypi.com>,
	Dom Cobley <dom@raspberrypi.com>,
	linux-doc@vger.kernel.org, Eric Anholt <eric@anholt.net>,
	Nicolas Saenz Julienne <nsaenzjulienne@kernel.org>,
	linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
	Maxime Ripard <mripard@kernel.org>,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	bcm-kernel-feedback-list@broadcom.com,
	linux-arm-kernel@lists.infradead.org,
	Daniel Vetter <daniel@ffwll.ch>,
	linux-rpi-kernel@lists.infradead.org,
	Jonathan Corbet <corbet@lwn.net>,
	Rob Herring <robh+dt@kernel.org>
Subject: Re: [PATCH v2 01/12] ALSA: doc: Clarify IEC958 controls iface
Date: Tue, 25 May 2021 17:58:29 +0200	[thread overview]
Message-ID: <s5ho8cybyai.wl-tiwai@suse.de> (raw)
In-Reply-To: <20210525132354.297468-2-maxime@cerno.tech>

On Tue, 25 May 2021 15:23:43 +0200,
Maxime Ripard wrote:
> 
> The doc currently mentions that the IEC958 Playback Default should be
> exposed on the PCM iface, and the Playback Mask on the mixer iface.
> 
> It's a bit confusing to advise to have two related controls on two
> separate ifaces, and it looks like the drivers that currently expose
> those controls use any combination of the mixer and PCM ifaces.
> 
> Let's try to clarify the situation a bit, and encourage to at least have
> the controls on the same iface.
> 
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>

Reviewed-by: Takashi Iwai <tiwai@suse.de>


thanks,

Takashi


> ---
>  .../sound/kernel-api/writing-an-alsa-driver.rst     | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
> index e6365836fa8b..01d59b8aea92 100644
> --- a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
> +++ b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst
> @@ -3508,14 +3508,15 @@ field must be set, though).
>  
>  “IEC958 Playback Con Mask” is used to return the bit-mask for the IEC958
>  status bits of consumer mode. Similarly, “IEC958 Playback Pro Mask”
> -returns the bitmask for professional mode. They are read-only controls,
> -and are defined as MIXER controls (iface =
> -``SNDRV_CTL_ELEM_IFACE_MIXER``).
> +returns the bitmask for professional mode. They are read-only controls.
>  
>  Meanwhile, “IEC958 Playback Default” control is defined for getting and
> -setting the current default IEC958 bits. Note that this one is usually
> -defined as a PCM control (iface = ``SNDRV_CTL_ELEM_IFACE_PCM``),
> -although in some places it's defined as a MIXER control.
> +setting the current default IEC958 bits.
> +
> +Due to historical reasons, both variants of the Playback Mask and the
> +Playback Default controls can be implemented on either a
> +``SNDRV_CTL_ELEM_IFACE_PCM`` or a ``SNDRV_CTL_ELEM_IFACE_MIXER`` iface.
> +Drivers should expose the mask and default on the same iface though.
>  
>  In addition, you can define the control switches to enable/disable or to
>  set the raw bit mode. The implementation will depend on the chip, but
> -- 
> 2.31.1
>