netdev - Re: [PATCH net] net: cdc_ncm: workaround for missing CDC Union

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Date:	Mon, 21 Jan 2013 15:55:05 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Bjørn Mork <bjorn@...k.no>
Cc:	Alexey Orishko <alexey.orishko@...il.com>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org, Greg Suarez <gsuarez@...thmicro.com>,
	Alexey Orishko <alexey.orishko@...ricsson.com>
Subject: Re: [PATCH net] net: cdc_ncm: workaround for missing CDC Union

On Monday 21 January 2013 15:47:13 Bjørn Mork wrote:
> But I wonder if this isn't really a generic problem in usbnet.  The
> FLAG_MULTI_PACKET test here seems completely bogus:
> 
>         if (length % dev->maxpacket == 0) {
>                 if (!(info->flags & FLAG_SEND_ZLP)) {
>                         if (!(info->flags & FLAG_MULTI_PACKET)) {
>                                 urb->transfer_buffer_length++;
>                                 if (skb_tailroom(skb)) {
>                                         skb->data[skb->len] = 0;
>                                         __skb_put(skb, 1);
>                                 }
>                         }
>                 } else
>                         urb->transfer_flags |= URB_ZERO_PACKET;
>         }
> 
> Either the FLAG_MULTI_PACKET minidriver will have already padded the
> buffer so that we do not hit (length % dev->maxpacket == 0), or we
> should choose one of the alternatives: ZLP or padding.

But we cannot simply call __skb_put for a complicated data frame.
Besides you may want the current behavior.

	Regards
		Oliver

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