net: Allow netdevices to specify needed head/tailroom

This patch adds needed_headroom/needed_tailroom members to struct
net_device and updates many places that allocate sbks to use them. Not
all of them can be converted though, and I'm sure I missed some (I
mostly grepped for LL_RESERVED_SPACE)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 2 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a3fb57fde623..b11e6e19e96c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -246,11 +246,16 @@ struct hh_cache
  *
  * We could use other alignment values, but we must maintain the
  * relationship HH alignment <= LL alignment.
+ *
+ * LL_ALLOCATED_SPACE also takes into account the tailroom the device
+ * may need.
  */
 #define LL_RESERVED_SPACE(dev) \
-        (((dev)->hard_header_len&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
+        ((((dev)->hard_header_len+(dev)->needed_headroom)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
 #define LL_RESERVED_SPACE_EXTRA(dev,extra) \
-        ((((dev)->hard_header_len+extra)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
+        ((((dev)->hard_header_len+(dev)->needed_headroom+(extra))&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
+#define LL_ALLOCATED_SPACE(dev) \
+        ((((dev)->hard_header_len+(dev)->needed_headroom+(dev)->needed_tailroom)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
 
 struct header_ops {
         int     (*create) (struct sk_buff *skb, struct net_device *dev,
@@ -569,6 +574,13 @@ struct net_device
         unsigned short          type;   /* interface hardware type      */
         unsigned short          hard_header_len;        /* hardware hdr length  */
 
+        /* extra head- and tailroom the hardware may need, but not in all cases
+         * can this be guaranteed, especially tailroom. Some cases also use
+         * LL_MAX_HEADER instead to allocate the skb.
+         */
+        unsigned short          needed_headroom;
+        unsigned short          needed_tailroom;
+
         struct net_device       *master; /* Pointer to master device of a group,
                                           * which this device is member of.
                                           */