What did the Buddha mean when he spoke about samma samadhi? What did the Buddha mean when he spoke about samma samadhi?
Did he mean access concentration (upacara samadhi) or full absorption (appana samadhi) or momentary concentration (khanika samadhi)?
The Suttas usually define Samma-Samadhi as the four jhanas, but in some Suttas it gives a different explanation. For example, in the Mahacattarisa Sutta the Buddha said:


  The Blessed One said: "Now what, monks, is noble right concentration
  with its supports &amp; requisite conditions? Any singleness of mind
  equipped with these seven factors — right view, right resolve, right
  speech, right action, right livelihood, right effort, &amp; right
  mindfulness — is called noble right concentration with its supports &amp;
  requisite conditions.
  
  (Source: http://www.accesstoinsight.org/tipitaka/mn/mn.117.than.html )


In the interpretation of the commentaries, any of the three levels of concentration can be sufficient, but in the case of momentary concentration, it would at least need to have the intensity of access concentration although it wouldn't have the duration of access concentration.