Am Freitag, 17. Dezember 2004 14:33 schrieb li xinyi:
> > >
> > > which piece of code initiated the DMA?
> >
> > I am not a specialist on ohci, but have a look at ohci_hub_resume()
> >
>
> I can not find explicit code which initialises DMA. Could it be
> pci_set_master?
pci_set_master() indeed allows a pci device to do DMA.
AFAIK you cannot use OHCI in PIO mode. You switch on DMA when you
enable traffic on the bus.
> > It dispatches among the drivers sharing a major number, but you are
> > not required to use the usb major.
> >
>
> But device drivers, e.g. usb-skeleton also register itself with
> USBMAJOR number. In this case, which code is called when user invoke
> open() with, for example, /dev/usb/skel? In which scenario, usb_open()
> is invoked?
usb_open will call the open method the driver provides with correct
module reference counting.
HTH
Oliver
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