Re: [v4] usb: UHCI: fix pkt size in TD for a sg element

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On Mon, 24 Jun 2013, Felipe Balbi wrote:

> BTW, EHCI can handle "short" SGs in the first page. See page 97 of EHCI
> 1.0 spec.

I'm not sure what you're talking about.  SG is used for bulk transfers, 
whereas p. 97 is about interrupt transfers.

It's true that the hardware's abilities aren't fully utilized by 
ehci-hcd.  But since other HCDs have even stronger restrictions, I 
don't see much point in trying to make ehci-hcd more capable.

Besides, what happens if the short SG element is in the middle of the 
transfer, rather than at the very beginning?  Or if the "short" first 
SG element starts at a page boundary and ends somewhere inside the 
page?

Alan Stern

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