Re: [alsa-devel] [PATCH v1 5/5] ALSA: hda - Add DP-MST support for NVIDIA codecs

[Takashi Iwai <tiwai@suse.de>]

On Thu, 14 Nov 2019 04:37:04 +0100,
Nikhil Mahale wrote:
> 
> @@ -3494,11 +3500,86 @@ static const struct drm_audio_component_audio_ops nvhdmi_audio_ops = {
>  	.master_unbind = generic_acomp_master_unbind,
>  };
>  
> +static int nvhdmi_find_pcm_slot(struct hdmi_spec *spec,
> +				struct hdmi_spec_per_pin *per_pin)
> +{
> +	int i;
> +
> +	/*
> +	 * generic_hdmi_build_pcms() allocates (num_nids + dev_num - 1)
> +	 * number of pcms.
> +	 *
> +	 * The per_pin of pin_nid_idx=n and dev_id=m prefers to get pcm-n if m==0.
> +	 * This guarantees that dynamic pcm assignments are compatible with the
> +	 * legacy static per_pin-pmc assignment that existed in the days before
> +	 * DP-MST.
> +	 *
> +	 * per_pin of m!=0 prefers to get pcm=(num_nids + (m - 1)).
> +	 */
> +	if (per_pin->dev_id == 0 &&
> +	    !test_bit(per_pin->pin_nid_idx, &spec->pcm_bitmap))
> +		return per_pin->pin_nid_idx;
> +
> +	if (per_pin->dev_id != 0 &&
> +	    !(test_bit(spec->num_nids + (per_pin->dev_id - 1),
> +		&spec->pcm_bitmap))) {
> +		return spec->num_nids + (per_pin->dev_id - 1);
> +	}
> +
> +	/* have a second try; check the area over num_nids */
> +	for (i = spec->num_nids; i < spec->pcm_used; i++) {
> +		if (!test_bit(i, &spec->pcm_bitmap))
> +			return i;
> +	}
> +
> +	/* the last try; check the empty slots in pins */
> +	for (i = 0; i < spec->num_nids; i++) {
> +		if (!test_bit(i, &spec->pcm_bitmap))
> +			return i;
> +	}
> +	return -EBUSY;
> +}

I think this can be applied for Intel case, too.  No need for creating
yet another indirect branch.


thanks,

Takashi
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