[PATCH 12/17] can: ems_usb: In ems_usb_start_xmit send only bytes with valid content to interface and not the complete buffer. Set first four bytes of buffer to 0. Wrapped long lines.

[Gerhard Uttenthaler <uttenthaler@xxxxxxxxxxxxxxxx>]

Signed-off-by: Gerhard Uttenthaler <uttenthaler@xxxxxxxxxxxxxxxx>
---
 drivers/net/can/usb/ems_usb.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/net/can/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
index b51a5eb65946..c464d644c833 100644
--- a/drivers/net/can/usb/ems_usb.c
+++ b/drivers/net/can/usb/ems_usb.c
@@ -902,25 +902,37 @@ static netdev_tx_t ems_usb_start_xmit(struct sk_buff *skb, struct net_device *ne
 	struct can_frame *cf = (struct can_frame *)skb->data;
 	struct ems_cpc_msg *msg;
 	struct urb *urb;
-	u8 *buf;
 	int i, err;
-	size_t size = CPC_HEADER_SIZE + CPC_MSG_HEADER_LEN
-			+ sizeof(struct cpc_can_msg);
+
+	u8 *buf;
+	size_t buf_size;
+	size_t buf_len = CPC_HEADER_SIZE + CPC_MSG_HEADER_LEN;
 
 	if (can_dropped_invalid_skb(netdev, skb))
 		return NETDEV_TX_OK;
 
-	/* create a URB, and a buffer for it, and copy the data to the URB */
+	buf_size = CPC_HEADER_SIZE +
+		   CPC_MSG_HEADER_LEN +
+		   sizeof(struct cpc_can_msg);
+
+	/* Create an URB, and a buffer for it
+	 * and copy the data to the URB
+	 */
 	urb = usb_alloc_urb(0, GFP_ATOMIC);
 	if (!urb)
 		goto nomem;
 
-	buf = usb_alloc_coherent(dev->udev, size, GFP_ATOMIC, &urb->transfer_dma);
+	buf = usb_alloc_coherent(dev->udev,
+				 buf_size,
+				 GFP_ATOMIC,
+				 &urb->transfer_dma);
 	if (!buf) {
 		netdev_err(netdev, "No memory left for USB buffer\n");
 		usb_free_urb(urb);
 		goto nomem;
 	}
+	// Clear first 4 bytes
+	*(u32 *)buf = 0;
 
 	msg = (struct ems_cpc_msg *)&buf[CPC_HEADER_SIZE];
 
@@ -942,6 +954,9 @@ static netdev_tx_t ems_usb_start_xmit(struct sk_buff *skb, struct net_device *ne
 		msg->length = CPC_CAN_MSG_MIN_SIZE + cf->can_dlc;
 	}
 
+	// Send only significant bytes of buffer
+	buf_len += msg->length;
+
 	for (i = 0; i < MAX_TX_URBS; i++) {
 		if (dev->tx_contexts[i].echo_index == MAX_TX_URBS) {
 			context = &dev->tx_contexts[i];
@@ -953,7 +968,7 @@ static netdev_tx_t ems_usb_start_xmit(struct sk_buff *skb, struct net_device *ne
 	 * allowed (MAX_TX_URBS).
 	 */
 	if (!context) {
-		usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
+		usb_free_coherent(dev->udev, buf_size, buf, urb->transfer_dma);
 		usb_free_urb(urb);
 
 		netdev_warn(netdev, "couldn't find free context\n");
@@ -966,7 +981,7 @@ static netdev_tx_t ems_usb_start_xmit(struct sk_buff *skb, struct net_device *ne
 	context->dlc = cf->can_dlc;
 
 	usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 2), buf,
-			  size, ems_usb_write_bulk_callback, context);
+			  buf_len, ems_usb_write_bulk_callback, context);
 	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 	usb_anchor_urb(urb, &dev->tx_submitted);
 
@@ -979,7 +994,7 @@ static netdev_tx_t ems_usb_start_xmit(struct sk_buff *skb, struct net_device *ne
 		can_free_echo_skb(netdev, context->echo_index);
 
 		usb_unanchor_urb(urb);
-		usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
+		usb_free_coherent(dev->udev, buf_size, buf, urb->transfer_dma);
 		dev_kfree_skb(skb);
 
 		atomic_dec(&dev->active_tx_urbs);
-- 
2.26.2

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