Wall or Nothing

Bodhidharma came from the West. Whether the Red-bearded Barbarian came from Persia, or Afghanistan, or somewhere else on the Silk Road, or if he did indeed come from south India is all conjecture. Some say that Bodhidharma's very existence is open to debate, and not "existence" in some metaphysical context.

Legend has it that he meditated for nine years consecutively, staring at the wall of a cave. Other than the wall, or a cushion, or a grass mat, maybe just a pile of stones, what might he have meditated on? And just why did he come from the West? (Oh, is that a cypress tree in your garden?)