I don't know what variant (Rev 1.x or Rev 2.x) I2S you are dealing with, but I suspect their DMA operations are at least 'very similar'. You will find my Rev 1.x setup here:
https://community.freescale.com/message/82190#82190
That is particularly set up to interleave/de-interleave six 16-bit audio channels from consecutive linear ping-pong buffers to their respective CoDecs thru I2S network mode. I believe the 'defines' there allow for reasonable customization (except whatever I missed!). The DMA minor-loop/major-loop format, with sophisticated counter-manipulation capabilities at each level, in conjunction with 'half loop' interrupts, allows this unattended data handling.