On Mon, Jun 27, 2005 at 06:48:06AM +1000, matthew green wrote:
   > 
   >    On Sun, Jun 26, 2005 at 09:53:51PM +0200, Manuel Bouyer wrote:
   >    > 
   >    > Right now, bus_dma(9) because it only knows the limitations of the bus
   >    > (e.g. the 16MB limit for ISA, or 4GB limit for 32bit PCI).
   >    
   >    Why not change the attachments for devices with broken bus interfaces
   >    to hang them off a fake "bus" that enforces the relevant DMA restrictions?
   >    
   >    After all, logically that's precisely how they are: they aren't on PCI,
   >    exactly, they're on a broken-bus-interface-"bus" behind the PCI (from
   >    the CPU's perspective) that enforces restrictions that PCI doesn't have.
   > 
   > 
   > i didn't think it was possible for a non-bus (and thus MD) driver to
   > provide it's own bus_dma_tag_t.
   
   I'm suggesting that we should create logical "bus" drivers to attach
   these devices to.  They wouldn't actually _do_ anything but act as
   a shim to set up bus_dma the right way; but they should be sufficient
   for that, no?


but how?  bus_dma is defined in <machine/bus.h> and afaik there is
no way to do what you are suggesting (without changing bus_dma.)


.mrg.