netdev - [PATCH 3/8] usbnet: smsc95xx: simplify tx

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Message-Id: <20181012083405.19246-4-ben.dooks@codethink.co.uk>
Date:   Fri, 12 Oct 2018 09:34:00 +0100
From:   Ben Dooks <ben.dooks@...ethink.co.uk>
To:     netdev@...r.kernel.org
Cc:     oneukum@...e.com, davem@...emloft.net, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kernel@...ts.codethink.co.uk,
        Ben Dooks <ben.dooks@...ethink.co.uk>
Subject: [PATCH 3/8] usbnet: smsc95xx: simplify tx_fixup code

The smsc95xx_tx_fixup is doing multiple calls to skb_push() to
put an 8-byte command header onto the packet. It would be easier
to do one skb_push() and then copy the data in once the push is
done.

We also make the code smaller by using proper unaligned puts for
the header. This merges in the CPU to LE32 conversion as well and
makes the whole sequence easier to understand hopefully.

Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
---
Since v1:
- Add alignment changes using put_unaligned_le32()
---
 drivers/net/usb/smsc95xx.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index cb19aea139d3..0c083d1b7f34 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -2006,6 +2006,7 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
 	bool csum = skb->ip_summed == CHECKSUM_PARTIAL;
 	int overhead = csum ? SMSC95XX_TX_OVERHEAD_CSUM : SMSC95XX_TX_OVERHEAD;
 	u32 tx_cmd_a, tx_cmd_b;
+	void *ptr;
 
 	/* We do not advertise SG, so skbs should be already linearized */
 	BUG_ON(skb_shinfo(skb)->nr_frags);
@@ -2019,6 +2020,9 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
 		return NULL;
 	}
 
+	tx_cmd_b = (u32)skb->len;
+	tx_cmd_a = tx_cmd_b | TX_CMD_A_FIRST_SEG_ | TX_CMD_A_LAST_SEG_;
+
 	if (csum) {
 		if (skb->len <= 45) {
 			/* workaround - hardware tx checksum does not work
@@ -2032,24 +2036,18 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
 			csum = false;
 		} else {
 			u32 csum_preamble = smsc95xx_calc_csum_preamble(skb);
-			skb_push(skb, 4);
-			cpu_to_le32s(&csum_preamble);
-			memcpy(skb->data, &csum_preamble, 4);
+			ptr = skb_push(skb, 4);
+			put_unaligned_le32(csum_preamble, ptr);
+
+			tx_cmd_a += 4;
+			tx_cmd_b += 4;
+			tx_cmd_b |= TX_CMD_B_CSUM_ENABLE;
 		}
 	}
 
-	skb_push(skb, 4);
-	tx_cmd_b = (u32)(skb->len - 4);
-	if (csum)
-		tx_cmd_b |= TX_CMD_B_CSUM_ENABLE;
-	cpu_to_le32s(&tx_cmd_b);
-	memcpy(skb->data, &tx_cmd_b, 4);
-
-	skb_push(skb, 4);
-	tx_cmd_a = (u32)(skb->len - 8) | TX_CMD_A_FIRST_SEG_ |
-		TX_CMD_A_LAST_SEG_;
-	cpu_to_le32s(&tx_cmd_a);
-	memcpy(skb->data, &tx_cmd_a, 4);
+	ptr = skb_push(skb, 8);
+	put_unaligned_le32(tx_cmd_a, ptr);
+	put_unaligned_le32(tx_cmd_b, ptr+4);
 
 	return skb;
 }
-- 
2.19.1