[OpenWrt-Devel] [PATCH] comgt: add ncm proto support

Conor O'Gorman i at conorogorman.net
Wed Oct 8 11:27:48 EDT 2014

On 08/10/14 11:00, John Crispin wrote:
> the e3267 that sami sent me works with this proto, but i am failing to
> get a DHCP addr. could someone with a ncm dongle please try this patch
> on top of latest trunk please and tell me if they are getting a dhcp addr ?

I had a similar problem with a Huawei device. It worked after removing 
some zero padding in the ncm driver.

In cdc_ncm.c, cdc_ncm_fill_tx_frame(), towards the end there is handling 
for Zero Length Packets (ZLP) and padding short packets. I removed the 
padding, and it worked. Are you testing 3.10 or 3.14? It's changed ever 
so slightly between them.

I am somewhat confused by the comment. It won't pad out short packets, 
but does make shortish packets long.

  * If collected data size is less or equal CDC_NCM_MIN_TX_PKT bytes,
  * we send buffers as it is. If we get more data, it would be more
  * efficient for USB HS mobile device with DMA engine to receive a full
  * size NTB, than canceling DMA transfer and receiving a short packet.
if (skb_out->len > CDC_NCM_MIN_TX_PKT)
         /* final zero padding */

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