+/*
+ * The mem2_dma "device".
+ *
+ * This device "owns" a pool of coherent MEM2 memory that can be shared among
+ * several devices requiring MEM2 DMA buffers, instead of dedicating specific
+ * pools for each device.
+ *
+ * A device can use the shared coherent MEM2 memory pool by calling
+ * wii_set_mem2_dma_constraints().
+ *
+ */
+
+struct mem2_dma {
+	struct platform_device *pdev;
+

The space there isn't neccessary.

+	dma_addr_t dma_base;

I think you need only one of them. You don't seem to use 'base'

+	void *base;
+	size_t size;
+};