From: "Russell McGuire" <rmcguire@videopresence.com>
To: <linuxppc-embedded@ozlabs.org>
Subject: NETdev driver question xxxx_type_trans()
Date: Fri, 22 Feb 2008 12:26:12 -0800 [thread overview]
Message-ID: <000001c87591$2b5a8740$6405a8c0@absolut> (raw)
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All,
A general and specific question on the behavior of netdev devices before
received sk_buff(s) get passed up to the kernel.
I am almost done creating / testing an HDLC device driver for the 83xx.
I have it working at a low level and was printing out skb_bufs before and
after TX and RX, to ensure data integrity.
Due to me having the print_skbbuf, AFTER the hdlc_type_trans(skb, ndev).
I thought I was continuously losing 14 bytes of data, after a little digging
I realized that the hdlc_type_trans() call
was shifting the skb->data pointer forward by 14 bytes. ????????
Is this corresponding to a 14 byte pad that the kernel stack adds before it
sends it down?
And why isn't the data length being shortened as a result after I call
hdlc_type_trans?
Anyway. I guess I am confused as to what this function was intended for, I
see there are other calls for eth_type_trans, so I imagine their usage is
similar.
When are they needed?
-Russ
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next reply other threads:[~2008-02-22 20:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-22 20:26 Russell McGuire [this message]
2008-02-22 20:39 ` NETdev driver question xxxx_type_trans() Andy Fleming
2008-02-22 23:48 ` Russell McGuire
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