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+=======================
+HD-Audio DP-MST Support
+=======================
+
+To support DP MST audio, HD Audio hdmi codec driver introduces virtual pin
+and dynamic pcm assignment.
+
+Virtual pin is an extension of per_pin. The most difference of DP MST
+from legacy is that DP MST introduces device entry. Each pin can contain
+several device entries. Each device entry behaves as a pin.
+
+As each pin may contain several device entries and each codec may contain
+several pins, if we use one pcm per per_pin, there will be many PCMs.
+The new solution is to create a few PCMs and to dynamically bind pcm to
+per_pin. Driver uses spec->dyn_pcm_assign flag to indicate whether to use
+the new solution.
+
+PCM
+===
+To be added
+
+Pin Initialization
+==================
+Each pin may have several device entries (virtual pins). On Intel platform,
+the device entries number is dynamically changed. If DP MST hub is connected,
+it is in DP MST mode, and the device entries number is 3. Otherwise, the
+device entries number is 1.
+
+To simplify the implementation, all the device entries will be initialized
+when bootup no matter whether it is in DP MST mode or not.
+
+Connection list
+===============
+DP MST reuses connection list code. The code can be reused because
+device entries on the same pin have the same connection list.
+
+This means DP MST gets the device entry connection list without the
+device entry setting.
+
+Jack
+====
+
+Presume:
+ - MST must be dyn_pcm_assign, and it is acomp (for Intel scenario);
+ - NON-MST may or may not be dyn_pcm_assign, it can be acomp or !acomp;
+
+So there are the following scenarios:
+ a. MST (&& dyn_pcm_assign && acomp)
+ b. NON-MST && dyn_pcm_assign && acomp
+ c. NON-MST && !dyn_pcm_assign && !acomp
+
+Below discussion will ignore MST and NON-MST difference as it doesn't
+impact on jack handling too much.
+
+Driver uses struct hdmi_pcm pcm[] array in hdmi_spec and snd_jack is
+a member of hdmi_pcm. Each pin has one struct hdmi_pcm * pcm pointer.
+
+For !dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] statically.
+
+For dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n]
+when monitor is hotplugged.
+
+
+Build Jack
+----------
+
+- dyn_pcm_assign
+
+  Will not use hda_jack but use snd_jack in spec->pcm_rec[pcm_idx].jack directly.
+
+- !dyn_pcm_assign
+
+  Use hda_jack and assign spec->pcm_rec[pcm_idx].jack = jack->jack statically.
+
+
+Unsolicited Event Enabling
+--------------------------
+Enable unsolicited event if !acomp.
+
+
+Monitor Hotplug Event Handling
+------------------------------
+- acomp
+
+  pin_eld_notify() -> check_presence_and_report() -> hdmi_present_sense() ->
+  sync_eld_via_acomp().
+
+  Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for
+  both dyn_pcm_assign and !dyn_pcm_assign
+
+- !acomp
+
+  hdmi_unsol_event() -> hdmi_intrinsic_event() -> check_presence_and_report() ->
+  hdmi_present_sense() -> hdmi_prepsent_sense_via_verbs()
+
+  Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for dyn_pcm_assign.
+  Use hda_jack mechanism to handle jack events.
+
+
+Others to be added later
+========================