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 (file)
--- a/drivers/net/wireless/rt2x00/rt2x00pci.c
+++ b/drivers/net/wireless/rt2x00/rt2x00pci.c
@@ -149,7 +149,7 @@ void rt2x00pci_rxdone(struct rt2x00_dev *rt2x00dev)
                 * 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 (file)
--- a/drivers/net/wireless/rt2x00/rt2x00usb.c
+++ b/drivers/net/wireless/rt2x00/rt2x00usb.c
@@ -245,13 +245,20 @@ static void rt2x00usb_interrupt_rxdone(struct urb *urb)
         * 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);
 
        /*