Re: [RFC 10/13] USB: Add macros for interrupt endpoint types.
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On Wed, 16 May 2012, Sarah Sharp wrote: > The USB 3.0 spec defines a new way of differentiating interrupt > endpoints. The idea is that some interrupt endpoints are used for > notifications, i.e. they continually NAK the transfer until something > changes on the device. Other interrupt endpoints are used (as they > should be, IMHO) as a way to periodically transfer data. > > The USB 3.0 endpoint descriptor uses bits 5:4 of bmAttributes for > interrupt endpoints, to define the endpoint as either a Notification > endpoint, or a Periodic endpoint. Introduce macros to dig out that > information. Do you know the reasoning behind this? Interrupt endpoints provide two things: guarantees on bandwidth and latency. The so-called Periodic endpoints rely mainly on the bandwidth guarantee, whereas the Notification endpoints rely on the latency guarantee. Either way, what difference does it make to the host controller or the system software? (And why do you think interrupt endpoints should always be of the Periodic type?) Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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