Re: User mode drivers: part 2: PCI device handling (patch 1/2 for 2.6.11)

From: Peter Chubb
Date: Sun Mar 13 2005 - 19:14:33 EST

>>>>> "Greg" == Greg KH <greg@xxxxxxxxx> writes:

Greg> On Fri, Mar 11, 2005 at 07:34:46PM +1100, Peter Chubb wrote:
>> >>>>> "Greg" == Greg KH <greg@xxxxxxxxx> writes:
Greg> On Fri, Mar 11, 2005 at 02:37:17PM +1100, Peter Chubb wrote:
>> >> +/* + * The PCI subsystem is implemented as yet-another pseudo
>> >> filesystem, + * albeit one that is never mounted. + * This is
>> its >> magic number. + */ +#define USR_PCI_MAGIC (0x12345678)
Greg> If you make it a real, mountable filesystem, then you don't need
Greg> to have any of your new syscalls, right? Why not just do that
Greg> instead?
>> The only call that would go is usr_pci_open() -- you'd still need
>> usr_pci_map()

Greg> see mmap(2)

mmap maps a file's contents into your own virtual memory.
usr_pci_map maps part of your own virtual memory into pci bus space
for a particular device (using the IOMMU if your machine has one), and
returns a scatterlist of bus addresses to hand to the device.

Different semantics entirely.

Greg> In fact, both of the above can be done today from /proc/bus/pci/
Greg> right?


Dr Peter Chubb peterc AT
The technical we do immediately, the political takes *forever*
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