Message ID | 1334916021-9124-1-git-send-email-inguin@gmx.de |
---|---|
State | Changes Requested, archived |
Delegated to: | David Miller |
Headers | show |
From: Ingo van Lil <inguin@gmx.de> Date: Fri, 20 Apr 2012 12:00:21 +0200 > - padlen = ((skb->len + 4) % 512) ? 0 : 4; > + padlen = ((skb->len + 4) % dev->maxpacket) ? 0 : 4; This is now an expensive modulus operation, instead of a cheap mask. Since you know that dev->maxpacket is always a power of two, tell the compiler this so it can still optimize the expression by changing this to "& (dev->maxpacket - 1)" and we'll thus avoid the costly modulus. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/usb/asix.c b/drivers/net/usb/asix.c index 5ee032c..aeb2702 100644 --- a/drivers/net/usb/asix.c +++ b/drivers/net/usb/asix.c @@ -355,7 +355,7 @@ static struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb, u32 packet_len; u32 padbytes = 0xffff0000; - padlen = ((skb->len + 4) % 512) ? 0 : 4; + padlen = ((skb->len + 4) % dev->maxpacket) ? 0 : 4; if ((!skb_cloned(skb)) && ((headroom + tailroom) >= (4 + padlen))) { @@ -377,7 +377,7 @@ static struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb, cpu_to_le32s(&packet_len); skb_copy_to_linear_data(skb, &packet_len, sizeof(packet_len)); - if ((skb->len % 512) == 0) { + if (padlen) { cpu_to_le32s(&padbytes); memcpy(skb_tail_pointer(skb), &padbytes, sizeof(padbytes)); skb_put(skb, sizeof(padbytes));
The asix.c USB Ethernet driver avoids ending a tx transfer with a zero- length packet by appending a four-byte padding to transfers whose length is a multiple of maxpacket. However, the hard-coded 512 byte maxpacket length is valid for high-speed USB only; full-speed USB uses 64 byte packets. Signed-off-by: Ingo van Lil <inguin@gmx.de> --- drivers/net/usb/asix.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)