30.01.2012 12:41, Chen Peter-B29397:
command stage, it will not prepare usb request. The gadget driver decides when
to send the data, the udc driver only supply callback function ->queue to help
prepare the request to hardware.
Hmmm. My understanding is that usb transfers are determined by host side
entirely (and this being a key point of the whole design). That is,
(-1-) transfer only (and always) starts as the host decides so, and
device just has to obey competely (or maybe NAK in the worst case).
On the other hand, I see that (-2-) the gadget attempts to behave much
like you say. That is, only send data if it has some.
I'm still failing to understand how can (-1-) and (-2-) be put together.
Thank you for your time, and my appologies for ignorant questions.
Nikolai
Also, what should host do if it did not receive neither NAK nor data?
There has to be some timeout probably? I've noticed that occasional 3
second delays still do not harm the transfer here (other than slowing it
down).
The host will do related operation according to usb class spec.
Thank you.
Nikolai
Thank you.
Nikolai
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