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

[Takashi Iwai]

On Wed, 21 Feb 2018 20:02:38 +0100,
Pierre-Louis Bossart wrote:
> 
> 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?

We can do that, too, but you don't know the mapping unless you really
plug, so it's a higher hurdle for users, I'm afraid.  Since most of
CHV/BYT devices are with a single output, this option is much easier
to deal with.


thanks,

Takashi

> 
> >
> > 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);
> >
>