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Posted: **Mon Jan 09, 2012 12:48 pm**

Hi guys!!

I'm working in a EHCI driver. Until now all just works!! Tried with sample DMA transferences, PCI interrupts, all is working quite good.

But I would know, how many QHs and QTd and similar structures would be fine to create when na USB device is attached?
And how many should be created at USB controller attach?

Thanks in advance guys!

Posted: **Wed Jan 11, 2012 1:17 pm**

I have one QH that points to itself for usb flash drive data transfers.
You might add additional QH into the circular link list for each usb device attached.
As for the QTd my driver is setup to transfer 512 bytes per TD so I divide the size of the qty bytes to be transferred by 512 to arrive at the number of TD's required in the chain.
I think you can transfer up to 4000 bytes per TD with ehci.

TomT
http://code.google.com/p/tatos/

Posted: **Fri Feb 03, 2012 2:21 pm**

That's sound good!! Thanks!
But if I have a 4 ports PCI controller for USB devices, how many QHs would be nice to create?

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EHCI number of QH and QTd?

EHCI number of QH and QTd?

Re: EHCI number of QH and QTd?

Re: EHCI number of QH and QTd?