linux-kernel - Re: [PATCH v6 2/4] drm: dw-hdmi-i2s: Use fixed id for codec device

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Message-ID: <1j7e663sfu.fsf@starbuckisacylon.baylibre.com>
Date:   Wed, 18 Sep 2019 10:43:49 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Cheng-Yi Chiang <cychiang@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Neil Armstrong <narmstrong@...libre.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jonas Karlman <jonas@...boo.se>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Heiko Stuebner <heiko@...ech.de>, dianders@...omium.org,
        dgreid@...omium.org, tzungbi@...omium.org,
        alsa-devel@...a-project.org, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v6 2/4] drm: dw-hdmi-i2s: Use fixed id for codec device


On Wed 18 Sep 2019 at 10:24, Cheng-Yi Chiang <cychiang@...omium.org> wrote:

> The problem of using auto ID is that the device name will be like
> hdmi-audio-codec.<id number>.auto.
>
> The number might be changed when there are other platform devices being
> created before hdmi-audio-codec device.
> Use a fixed name so machine driver can set codec name on the DAI link.
>
> Using the fixed name should be fine because there will only be one
> hdmi-audio-codec device.

While this is true all platforms we know of (I suppose), It might not be
the case later on. I wonder if making such assumption is really
desirable in a code which is used by quite a few different platforms.

Instead of trying to predict what the device name will be, can't you just
query it in your machine driver ? Using a device tree phandle maybe ?

It is quite usual to set the dai links this way, "simple-card" is a good
example of this.

>
> Fix the codec name in rockchip rk3288_hdmi_analog machine driver.
>
> Signed-off-by: Cheng-Yi Chiang <cychiang@...omium.org>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c | 2 +-
>  sound/soc/rockchip/rk3288_hdmi_analog.c             | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> index d7e65c869415..86bd482b9f94 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> @@ -193,7 +193,7 @@ static int snd_dw_hdmi_probe(struct platform_device *pdev)
>  
>  	memset(&pdevinfo, 0, sizeof(pdevinfo));
>  	pdevinfo.parent		= pdev->dev.parent;
> -	pdevinfo.id		= PLATFORM_DEVID_AUTO;
> +	pdevinfo.id		= PLATFORM_DEVID_NONE;
>  	pdevinfo.name		= HDMI_CODEC_DRV_NAME;
>  	pdevinfo.data		= &pdata;
>  	pdevinfo.size_data	= sizeof(pdata);
> diff --git a/sound/soc/rockchip/rk3288_hdmi_analog.c b/sound/soc/rockchip/rk3288_hdmi_analog.c
> index 767700c34ee2..8286025a8747 100644
> --- a/sound/soc/rockchip/rk3288_hdmi_analog.c
> +++ b/sound/soc/rockchip/rk3288_hdmi_analog.c
> @@ -15,6 +15,7 @@
>  #include <linux/gpio.h>
>  #include <linux/of_gpio.h>
>  #include <sound/core.h>
> +#include <sound/hdmi-codec.h>
>  #include <sound/jack.h>
>  #include <sound/pcm.h>
>  #include <sound/pcm_params.h>
> @@ -142,7 +143,7 @@ static const struct snd_soc_ops rk_ops = {
>  SND_SOC_DAILINK_DEFS(audio,
>  	DAILINK_COMP_ARRAY(COMP_EMPTY()),
>  	DAILINK_COMP_ARRAY(COMP_CODEC(NULL, NULL),
> -			   COMP_CODEC("hdmi-audio-codec.2.auto", "i2s-hifi")),
> +			   COMP_CODEC(HDMI_CODEC_DRV_NAME, "i2s-hifi")),
>  	DAILINK_COMP_ARRAY(COMP_EMPTY()));
>  
>  static struct snd_soc_dai_link rk_dailink = {