From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Date: Wed, 26 May 2010 21:44:19 +0000 (-0700)
Subject: Documentation: add networking driver's mapping error handling to DMA-API-HOWTO
X-Git-Tag: v2.6.35-rc1~93
X-Git-Url: http://bbs.cooldavid.org/git/?a=commitdiff_plain;h=f671be04dcda09f8383ae26072c0e75a79090193;p=net-next-2.6.git

Documentation: add networking driver's mapping error handling to DMA-API-HOWTO

Adds the concrete DMA mapping error handling for Networking drivers on the
transmit path.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index 2e435adfbd6..93d90870791 100644
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -740,6 +740,11 @@ failure can be determined by:
 		 */
 	}
 
+Networking drivers must call dev_kfree_skb to free the socket buffer
+and return NETDEV_TX_OK if the DMA mapping fails on the transmit hook
+(ndo_start_xmit). This means that the socket buffer is just dropped in
+the failure case.
+
 			   Closing
 
 This document, and the API itself, would not be in its current