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Date:   Tue, 25 May 2021 11:27:34 +0200
Message-ID: <s5hpmxfcge1.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     Mark Brown <broonie@kernel.org>, Takashi Iwai <tiwai@suse.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Jaroslav Kysela <perex@perex.cz>,
        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>,
        devicetree@vger.kernel.org, alsa-devel@alsa-project.org,
        Dom Cobley <dom@raspberrypi.com>,
        Tim Gover <tim.gover@raspberrypi.com>,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        linux-kernel@vger.kernel.org, Eric Anholt <eric@anholt.net>,
        Rob Herring <robh+dt@kernel.org>,
        bcm-kernel-feedback-list@broadcom.com,
        Nicolas Saenz Julienne <nsaenzjulienne@kernel.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        Phil Elwell <phil@raspberrypi.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-rpi-kernel@lists.infradead.org
Subject: Re: [PATCH 00/11] drm/vc4: hdmi: Enable Channel Mapping, IEC958, HBR Passthrough using hdmi-codec
In-Reply-To: <20210525092353.mvqdv4bi4i4rkqsu@gilmour>
References: <20210507140334.204865-1-maxime@cerno.tech>
        <20210524133904.kgkh6xd3m5c2j3xa@gilmour>
        <s5hzgwjcit9.wl-tiwai@suse.de>
        <20210525092353.mvqdv4bi4i4rkqsu@gilmour>
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On Tue, 25 May 2021 11:23:53 +0200,
Maxime Ripard wrote:
> 
> Hi Takashi,
> 
> On Tue, May 25, 2021 at 10:35:14AM +0200, Takashi Iwai wrote:
> > On Mon, 24 May 2021 15:39:04 +0200,
> > Maxime Ripard wrote:
> > > 
> > > Hi,
> > > 
> > > On Fri, May 07, 2021 at 04:03:23PM +0200, Maxime Ripard wrote:
> > > > Hi,
> > > > 
> > > > hdmi-codec allows to have a lot of HDMI-audio related infrastructure in place,
> > > > it's missing a few controls to be able to provide HBR passthrough. This series
> > > > adds more infrastructure for the drivers, and leverages it in the vc4 HDMI
> > > > controller driver.
> > > > 
> > > > One thing that felt a bit weird is that even though
> > > > https://www.kernel.org/doc/html/latest/sound/kernel-api/writing-an-alsa-driver.html#iec958-s-pdif
> > > > mentions that the iec958 mask control should be a mixer control and the
> > > > default control should be a PCM one, it feels a bit weird to have two different
> > > > control type for two controls so similar, and other drivers are pretty
> > > > inconsistent with this. Should we update the documentation?
> > > 
> > > Any comments on this series?
> > 
> > A patch for updating the documentation is welcome.
> > Currently, as de facto standard, we allow both MIXER and PCM ifaces
> > for all IEC958-related controls, and it's unlikely that we would
> > change that in future.
> 
> Ok, I'll write a patch for the documentation make it clearer then :)
> 
> Do we want to make sure that all the iec958 controls are on the same
> iface, or is it also left to the driver (or should we just leave the
> existing drivers as is but encourage a consistent use in the future)?

I'd leave the existing drivers as-is.  Changing the iface is basically
an incompatible change, and although most of applications and alsa-lib
should look at both ifaces, there can be any surprise by that change.


thanks,

Takashi