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Re: take 2: MI overrides of bus_dma(9), bus_space(9), pci(9)

On Thursday 08 April 2010 02:10:28 David Young wrote:
> I would like for MI drivers to be able to override pci(9), bus_space(9),
> and bus_dma(9) behavior for the purpose of handling exceptions, managing
> bus resources, creating test harnesses, and counting events.
> Matt Thomas nudged me in some private discussions to leave MD the
> bus_space_tag_t and pci_chipset_tag_t, instead of embedding an MI tag,
> and to let each architecture provide its own implementation of an
> MI override functions for bus_space(9) and pci(9).  Matt powerfully
> influenced the look of the override API.


If for example a PCI device is behind an USB interface, should the bus space 
methods take a mutex argument to allow sleeping which is due to the fact that 
USB cannot complete the I/O operation immediately?


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