rt2x00: Fix ieee80211 payload alignment
As Johannes Berg indicated, the NET_IP_ALIGN doesn't
need to be used for ieee80211 frames. This means we
can simplify the alignment calculation to just
use the result of the header size modulus 4 as frame
alignment.
Furthermore we shouldn't use NET_IP_ALIGN in rt2x00usb
because it could be 0 on some architectures and we absolutely
need to have 2 bytes reserved for possible aligning.
Signed-off-by: Ivo van Doorn<IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00pci.c b/drivers/net/wireless/rt2x00/rt2x00pci.c
index 6d5d9ab..04663eb 100644
--- a/drivers/net/wireless/rt2x00/rt2x00pci.c
+++ b/drivers/net/wireless/rt2x00/rt2x00pci.c
@@ -149,7 +149,7 @@
* The data behind the ieee80211 header must be
* aligned on a 4 byte boundary.
*/
- align = NET_IP_ALIGN + (2 * (header_size % 4 == 0));
+ align = header_size % 4;
/*
* Allocate the sk_buffer, initialize it and copy
diff --git a/drivers/net/wireless/rt2x00/rt2x00usb.c b/drivers/net/wireless/rt2x00/rt2x00usb.c
index ab4797e..568d738 100644
--- a/drivers/net/wireless/rt2x00/rt2x00usb.c
+++ b/drivers/net/wireless/rt2x00/rt2x00usb.c
@@ -245,13 +245,20 @@
* Allocate a new sk buffer to replace the current one.
* If allocation fails, we should drop the current frame
* so we can recycle the existing sk buffer for the new frame.
+ * As alignment we use 2 and not NET_IP_ALIGN because we need
+ * to be sure we have 2 bytes room in the head. (NET_IP_ALIGN
+ * can be 0 on some hardware). We use these 2 bytes for frame
+ * alignment later, we assume that the chance that
+ * header_size % 4 == 2 is bigger then header_size % 2 == 0
+ * and thus optimize alignment by reserving the 2 bytes in
+ * advance.
*/
frame_size = entry->ring->data_size + entry->ring->desc_size;
- skb = dev_alloc_skb(frame_size + NET_IP_ALIGN);
+ skb = dev_alloc_skb(frame_size + 2);
if (!skb)
goto skip_entry;
- skb_reserve(skb, NET_IP_ALIGN);
+ skb_reserve(skb, 2);
skb_put(skb, frame_size);
/*