Attached is a patch which moves dma_mask into struct device and cleans up the 
scsi mid-layer to use it (instead of using struct pci_dev).  The advantage to 
doing this is probably most apparent on non-pci bus architectures where 
currently you have to construct a fake pci_dev just so you can get the bounce 
buffers to work correctly.
  
The patch tries to perturb the minimum amount of code, so dma_mask in struct 
device is simply a pointer to the one in pci_dev.  However, it will make it 
easy for me now to add generic device to MCA without having to go the fake pci
route.