On Tue, 6 Sep 2005, Franck wrote:

> > > Can you point out in the code where is the setup of 4 times per second
> > > interval ? I can't find it.
> > 
> > It's in drivers/usb/core/hub.c.  The URB is set up near the end of
> > hub_configure(), and it is submitted in hub_activate().  Search for
> > occurrences of "hub->urb".  The requested period is endpoint->bInterval,
> > taken from the hub's endpoint descriptor.
> > 
> 
> Thanks Alan for your answer, but I was looking at the part which send
> a "get endpoint descriptor" request and setup "endpoint->bInterval"

(There is no such thing as a "get endpoint descriptor" request.  Endpoint
descriptors are sent as part of the reply to a Get-Configuration request. 
See section 9.4.3 of the USB 2.0 spec.)

The "get endpoint descriptor" part is done in drivers/usb/core/config.c, 
mostly in usb_parse_endpoint().  The actual transfer of the descriptor 
from the device is done in usb_get_configuration(), at the end of the same 
source file.

endpoint->bInterval isn't set up anywhere.  It's part of the data received 
from the device in response to the Get-Configuration request.

Alan Stern



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