netdev - Re: changing usbnet's API to better deal with cdc-ncm

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Date:	Fri, 7 Sep 2012 20:58:25 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Alexey ORISHKO <alexey.orishko@...ricsson.com>
Cc:	Oliver Neukum <oneukum@...e.de>, "bjorn@...k.no" <bjorn@...k.no>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Alexey Orishko <alexey.orishko@...il.com>
Subject: Re: changing usbnet's API to better deal with cdc-ncm

On Thu, Sep 6, 2012 at 4:13 PM, Alexey ORISHKO
<alexey.orishko@...ricsson.com> wrote:
>> -----Original Message-----
>> From: Oliver Neukum [mailto:oneukum@...e.de]
>
>
>> looking at cdc-ncm it seeems to me that cdc-ncm is forced to play very
>> dirty games because usbnet doesn't have a notion about aggregating
>> packets for a single transfer.
>
> Several issues need to be improved:
> Tx path:
> 1. IP packets must be accumulated in one NTB. Currently it's done via data copy.
> Preferred way would be a possibility to have a list of skb-s in resulting frame sent down.

Looks the copy is inevitable because the buffer length of each skb in the
list is not possible to be max endpoint packet aligned, so one short packet
may terminate the current tx urb transfer.


Thanks,
-- 
Ming Lei
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