linux-kernel - Re: [PATCH 00/11] drm/vc4: hdmi: Enable Channel Mapping, IEC958, HBR Passthrough using hdmi-codec

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Message-ID: <20210525092353.mvqdv4bi4i4rkqsu@gilmour>
Date:   Tue, 25 May 2021 11:23:53 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        devicetree@...r.kernel.org, alsa-devel@...a-project.org,
        Dom Cobley <dom@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-kernel@...r.kernel.org, Eric Anholt <eric@...olt.net>,
        Rob Herring <robh+dt@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        Nicolas Saenz Julienne <nsaenzjulienne@...nel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Phil Elwell <phil@...pberrypi.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH 00/11] drm/vc4: hdmi: Enable Channel Mapping, IEC958, HBR
 Passthrough using hdmi-codec

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)?

Maxime

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