[alsa-devel] [PATCH] ALSA: x86: hdmi: Add single_port option for compatible behavior

[Pierre-Louis Bossart]

On 2/21/18 9:53 AM, Takashi Iwai wrote:
> The recent support for the multiple PCM devices allowed user to use
> multiple HDMI/DP outputs, but at the same time, the PCM stream
> assignment has been changed, too.  Due to that, the former PCM#0
> (there was only one stream in the past) is likely assigned to a
> different one (e.g. PCM#2), and it ends up with the regression when
> user sticks with the fixed configuration using the device#0.
> 
> Although the multiple monitor support shouldn't matter when user
> deploys the backend like PulseAudio that checks the jack detection
> state, the behavior change isn't always acceptable for some users.
> 
> As a mitigation, this patch introduces an option to switch the
> behavior back to the old-good-days: when the new option,
> single_port=1, is passed, the driver creates only a single PCM device,
> and it's assigned to the first connected one, like the earlier
> versions did.  The option is turned off as default still to support
> the multiple monitors.

Sounds ok, but would it makes sense to instead of a scalar single-port 
argument use a look-up table with more values, e.g. with an argument of 
(2,0,1), the port 0 would be PCM2, port 1 PCM0 and port 2 PCM1?

> 
> Fixes: 8a2d6ae1f737 ("ALSA: x86: Register multiple PCM devices for the LPE audio card")
> Reported-and-tested-by: Hubert Mantel <mantel at metadox.de>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>   sound/x86/intel_hdmi_audio.c | 14 +++++++++++---
>   1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/x86/intel_hdmi_audio.c b/sound/x86/intel_hdmi_audio.c
> index a0951505c7f5..96115c401292 100644
> --- a/sound/x86/intel_hdmi_audio.c
> +++ b/sound/x86/intel_hdmi_audio.c
> @@ -50,6 +50,7 @@
>   /*standard module options for ALSA. This module supports only one card*/
>   static int hdmi_card_index = SNDRV_DEFAULT_IDX1;
>   static char *hdmi_card_id = SNDRV_DEFAULT_STR1;
> +static bool single_port;
>   
>   module_param_named(index, hdmi_card_index, int, 0444);
>   MODULE_PARM_DESC(index,
> @@ -57,6 +58,9 @@ MODULE_PARM_DESC(index,
>   module_param_named(id, hdmi_card_id, charp, 0444);
>   MODULE_PARM_DESC(id,
>   		"ID string for INTEL Intel HDMI Audio controller.");
> +module_param(single_port, bool, 0444);
> +MODULE_PARM_DESC(single_port,
> +		"Single-port mode (for compatibility)");
>   
>   /*
>    * ELD SA bits in the CEA Speaker Allocation data block
> @@ -1579,7 +1583,11 @@ static irqreturn_t display_pipe_interrupt_handler(int irq, void *dev_id)
>   static void notify_audio_lpe(struct platform_device *pdev, int port)
>   {
>   	struct snd_intelhad_card *card_ctx = platform_get_drvdata(pdev);
> -	struct snd_intelhad *ctx = &card_ctx->pcm_ctx[port];
> +	struct snd_intelhad *ctx;
> +
> +	ctx = &card_ctx->pcm_ctx[single_port ? 0 : port];
> +	if (single_port)
> +		ctx->port = port;
>   
>   	schedule_work(&ctx->hdmi_audio_wq);
>   }
> @@ -1816,7 +1824,7 @@ static int hdmi_lpe_audio_probe(struct platform_device *pdev)
>   	init_channel_allocations();
>   
>   	card_ctx->num_pipes = pdata->num_pipes;
> -	card_ctx->num_ports = pdata->num_ports;
> +	card_ctx->num_ports = single_port ? 1 : pdata->num_ports;
>   
>   	for_each_port(card_ctx, port) {
>   		struct snd_intelhad *ctx = &card_ctx->pcm_ctx[port];
> @@ -1824,7 +1832,7 @@ static int hdmi_lpe_audio_probe(struct platform_device *pdev)
>   
>   		ctx->card_ctx = card_ctx;
>   		ctx->dev = card_ctx->dev;
> -		ctx->port = port;
> +		ctx->port = single_port ? -1 : port;
>   		ctx->pipe = -1;
>   
>   		INIT_WORK(&ctx->hdmi_audio_wq, had_audio_wq);
>