[alsa-devel] [RFC PATCH] ASoC: codec: hdac_hdmi: no checking monitor in hw_params

[Pierre-Louis Bossart]

On 5/6/19 1:59 AM, libin.yang at intel.com wrote:
> From: Libin Yang <libin.yang at intel.com>
> 
> This patch move the check of monitor from hw_params to trigger callback.
> 
> The original code will check the monitor presence in hw_params. If the
> monitor doesn't exist, hw_params will return -ENODEV. Mostly this is OK.
> 
> However, pulseaudio will check the pcm devices when kernel is booting up.
> It will try to open, set hw_params, prepare such pcm devices. We can't
> guarantee that the monitor will be connected when kernel is booting up.
> Especially, hdac_hdmi will export 3 pcms at most. It's hard to say users
> will connect 3 monitors to the HDMI/DP ports. This will cause pulseaudio
> fail in parsing the pcm devices because the driver will return -ENODEV in
> hw_params.
> 
> This patch tries to move the check of monitor presence into trigger
> callback. This can "trick" the pulseaudio the pcm is ready.
> 
> This bug is found when we try to enable HDMI detection in
> gnome-sound-setting for ASoC hdac_hdmi. After we enable the hdmi in UCM,
> pulseaudio will try to parse the hdmi pcm devices. It will cause failure if
> there are no monitors connected.

Out of curiosity, how is this handled in the legacy driver? I haven't 
done this for a long time but I remember very clearly being able to play 
on the HDMI:3,7, etc devices without any monitors connected. You'd get 
of course no sound but there was no error reported to userspace. The 
hardware is perfectly capable of pushing samples into the display 
controller using the HDAudio/iDisp link.

> 
> Signed-off-by: Libin Yang <libin.yang at intel.com>
> ---
>   sound/soc/codecs/hdac_hdmi.c | 44 +++++++++++++++++++++++++++++++-------------
>   1 file changed, 31 insertions(+), 13 deletions(-)
> 
> diff --git a/sound/soc/codecs/hdac_hdmi.c b/sound/soc/codecs/hdac_hdmi.c
> index 4de1fbf..f482e09 100644
> --- a/sound/soc/codecs/hdac_hdmi.c
> +++ b/sound/soc/codecs/hdac_hdmi.c
> @@ -455,24 +455,11 @@ static int hdac_hdmi_set_hw_params(struct snd_pcm_substream *substream,
>   	struct snd_pcm_hw_params *hparams, struct snd_soc_dai *dai)
>   {
>   	struct hdac_hdmi_priv *hdmi = snd_soc_dai_get_drvdata(dai);
> -	struct hdac_device *hdev = hdmi->hdev;
>   	struct hdac_hdmi_dai_port_map *dai_map;
> -	struct hdac_hdmi_port *port;
>   	struct hdac_hdmi_pcm *pcm;
>   	int format;
>   
>   	dai_map = &hdmi->dai_map[dai->id];
> -	port = dai_map->port;
> -
> -	if (!port)
> -		return -ENODEV;
> -
> -	if ((!port->eld.monitor_present) || (!port->eld.eld_valid)) {
> -		dev_err(&hdev->dev,
> -			"device is not configured for this pin:port%d:%d\n",
> -					port->pin->nid, port->id);
> -		return -ENODEV;
> -	}
>   
>   	format = snd_hdac_calc_stream_format(params_rate(hparams),
>   			params_channels(hparams), params_format(hparams),
> @@ -630,6 +617,36 @@ static void hdac_hdmi_pcm_close(struct snd_pcm_substream *substream,
>   		dai_map->port = NULL;
>   }
>   
> +static int hdac_hdmi_pcm_trigger(struct snd_pcm_substream *substream, int cmd,
> +				 struct snd_soc_dai *dai)
> +{
> +	struct hdac_hdmi_port *port;
> +	struct hdac_hdmi_dai_port_map *dai_map;
> +	struct hdac_hdmi_priv *hdmi = snd_soc_dai_get_drvdata(dai);
> +	struct hdac_device *hdev = hdmi->hdev;
> +
> +	/*
> +	 * When start, if there is no monitor,
> +	 * It should not start audio.
> +	 */
> +	if (cmd == SNDRV_PCM_TRIGGER_START) {
> +		dai_map = &hdmi->dai_map[dai->id];
> +		port = dai_map->port;
> +
> +		if (!port)
> +			return -ENODEV;
> +
> +		if ((!port->eld.monitor_present) || (!port->eld.eld_valid)) {
> +			dev_err(&hdev->dev,
> +				"device is not configured for this pin:port%d:%d\n",
> +				port->pin->nid, port->id);
> +			return -ENODEV;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>   static int
>   hdac_hdmi_query_cvt_params(struct hdac_device *hdev, struct hdac_hdmi_cvt *cvt)
>   {
> @@ -1389,6 +1406,7 @@ static const struct snd_soc_dai_ops hdmi_dai_ops = {
>   	.startup = hdac_hdmi_pcm_open,
>   	.shutdown = hdac_hdmi_pcm_close,
>   	.hw_params = hdac_hdmi_set_hw_params,
> +	.trigger = hdac_hdmi_pcm_trigger,
>   	.set_tdm_slot = hdac_hdmi_set_tdm_slot,
>   };
>   
>