On Sat, 3 Aug 2013, Ming Lei wrote:
> Some host controllers(such as xHCI) can support building
> packet from discontinuous buffers, so introduce one flag
> and helper for this kind of host controllers, then the
> feature can help some applications(such as, usbnet) by
> supporting arbitrary length of sg buffers.
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index 84f14e2..5d03074 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -337,6 +337,7 @@ struct usb_bus {
> * the ep queue on a short transfer
> * with the URB_SHORT_NOT_OK flag set.
> */
> + unsigned no_sg_limit:1; /* no sg list limit */
Why do you call this "no_sg_limit"? It isn't a limit on the SG list;
the list can be arbitrarily long, provided all the entries except the
last are divisible by the maxpacket size.
You could call it "no_sg_constraint" if you want. Or
"allow_arbitrary_sg", to put a more positive spin on it.
Alan Stern
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