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

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