[v5] wwan: core: Support slicing in port TX flow of WWAN subsystem

diff --git a/drivers/net/wwan/iosm/iosm_ipc_port.c b/drivers/net/wwan/iosm/iosm_ipc_port.c
index b6d81c627277..7798348f61d0 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_port.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_port.c
@@ -63,7 +63,8 @@  struct iosm_cdev *ipc_port_init(struct iosm_imem *ipc_imem,
 	ipc_port->ipc_imem = ipc_imem;
 
 	ipc_port->iosm_port = wwan_create_port(ipc_port->dev, port_type,
-					       &ipc_wwan_ctrl_ops, ipc_port);
+					       &ipc_wwan_ctrl_ops, WWAN_NO_FRAGMENT,
+					       WWAN_NO_HEADROOM, ipc_port);
 
 	return ipc_port;
 }
diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index f7ca52353f40..c397aa53db5d 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -237,7 +237,8 @@  static int mhi_wwan_ctrl_probe(struct mhi_device *mhi_dev,
 
 	/* Register as a wwan port, id->driver_data contains wwan port type */
 	port = wwan_create_port(&cntrl->mhi_dev->dev, id->driver_data,
-				&wwan_pops, mhiwwan);
+				&wwan_pops, WWAN_NO_FRAGMENT, WWAN_NO_HEADROOM,
+				mhiwwan);
 	if (IS_ERR(port)) {
 		kfree(mhiwwan);
 		return PTR_ERR(port);
diff --git a/drivers/net/wwan/rpmsg_wwan_ctrl.c b/drivers/net/wwan/rpmsg_wwan_ctrl.c
index 31c24420ab2e..fc6c228b7e1c 100644
--- a/drivers/net/wwan/rpmsg_wwan_ctrl.c
+++ b/drivers/net/wwan/rpmsg_wwan_ctrl.c
@@ -129,7 +129,8 @@  static int rpmsg_wwan_ctrl_probe(struct rpmsg_device *rpdev)
 
 	/* Register as a wwan port, id.driver_data contains wwan port type */
 	port = wwan_create_port(parent, rpdev->id.driver_data,
-				&rpmsg_wwan_pops, rpwwan);
+				&rpmsg_wwan_pops, WWAN_NO_FRAGMENT,
+				WWAN_NO_HEADROOM, rpwwan);
 	if (IS_ERR(port))
 		return PTR_ERR(port);
 
diff --git a/drivers/net/wwan/t7xx/t7xx_port_wwan.c b/drivers/net/wwan/t7xx/t7xx_port_wwan.c
index 33931bfd78fd..b75bb272f861 100644
--- a/drivers/net/wwan/t7xx/t7xx_port_wwan.c
+++ b/drivers/net/wwan/t7xx/t7xx_port_wwan.c
@@ -54,13 +54,13 @@  static void t7xx_port_ctrl_stop(struct wwan_port *port)
 static int t7xx_port_ctrl_tx(struct wwan_port *port, struct sk_buff *skb)
 {
 	struct t7xx_port *port_private = wwan_port_get_drvdata(port);
-	size_t len, offset, chunk_len = 0, txq_mtu = CLDMA_MTU;
 	const struct t7xx_port_conf *port_conf;
+	struct sk_buff *cur = skb, *cloned;
 	struct t7xx_fsm_ctl *ctl;
 	enum md_state md_state;
+	int cnt = 0, ret;
 
-	len = skb->len;
-	if (!len || !port_private->chan_enable)
+	if (!port_private->chan_enable)
 		return -EINVAL;
 
 	port_conf = port_private->port_conf;
@@ -72,23 +72,21 @@  static int t7xx_port_ctrl_tx(struct wwan_port *port, struct sk_buff *skb)
 		return -ENODEV;
 	}
 
-	for (offset = 0; offset < len; offset += chunk_len) {
-		struct sk_buff *skb_ccci;
-		int ret;
-
-		chunk_len = min(len - offset, txq_mtu - sizeof(struct ccci_header));
-		skb_ccci = t7xx_port_alloc_skb(chunk_len);
-		if (!skb_ccci)
-			return -ENOMEM;
-
-		skb_put_data(skb_ccci, skb->data + offset, chunk_len);
-		ret = t7xx_port_send_skb(port_private, skb_ccci, 0, 0);
+	while (cur) {
+		cloned = skb_clone(cur, GFP_KERNEL);
+		cloned->len = skb_headlen(cur);
+		ret = t7xx_port_send_skb(port_private, cloned, 0, 0);
 		if (ret) {
-			dev_kfree_skb_any(skb_ccci);
+			dev_kfree_skb(cloned);
 			dev_err(port_private->dev, "Write error on %s port, %d\n",
 				port_conf->name, ret);
-			return ret;
+			return cnt ? cnt + ret : ret;
 		}
+		cnt += cur->len;
+		if (cur == skb)
+			cur = skb_shinfo(skb)->frag_list;
+		else
+			cur = cur->next;
 	}
 
 	dev_kfree_skb(skb);
@@ -154,13 +152,15 @@  static int t7xx_port_wwan_disable_chl(struct t7xx_port *port)
 static void t7xx_port_wwan_md_state_notify(struct t7xx_port *port, unsigned int state)
 {
 	const struct t7xx_port_conf *port_conf = port->port_conf;
+	unsigned int header_len = sizeof(struct ccci_header);
 
 	if (state != MD_STATE_READY)
 		return;
 
 	if (!port->wwan_port) {
 		port->wwan_port = wwan_create_port(port->dev, port_conf->port_type,
-						   &wwan_ops, port);
+						   &wwan_ops, CLDMA_MTU - header_len,
+						   header_len, port);
 		if (IS_ERR(port->wwan_port))
 			dev_err(port->dev, "Unable to create WWWAN port %s", port_conf->name);
 	}
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 62e9f7d6c9fe..8d35513bcd4c 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -67,6 +67,8 @@  struct wwan_device {
  * @rxq: Buffer inbound queue
  * @waitqueue: The waitqueue for port fops (read/write/poll)
  * @data_lock: Port specific data access serialization
+ * @headroom_len: SKB reserved headroom size
+ * @frag_len: Length to fragment packet
  * @at_data: AT port specific data
  */
 struct wwan_port {
@@ -79,6 +81,8 @@  struct wwan_port {
 	struct sk_buff_head rxq;
 	wait_queue_head_t waitqueue;
 	struct mutex data_lock;	/* Port specific data access serialization */
+	size_t headroom_len;
+	size_t frag_len;
 	union {
 		struct {
 			struct ktermios termios;
@@ -422,6 +426,8 @@  static int __wwan_port_dev_assign_name(struct wwan_port *port, const char *fmt)
 struct wwan_port *wwan_create_port(struct device *parent,
 				   enum wwan_port_type type,
 				   const struct wwan_port_ops *ops,
+				   size_t frag_len,
+				   unsigned int headroom_len,
 				   void *drvdata)
 {
 	struct wwan_device *wwandev;
@@ -455,6 +461,8 @@  struct wwan_port *wwan_create_port(struct device *parent,
 
 	port->type = type;
 	port->ops = ops;
+	port->frag_len = frag_len ? frag_len : SIZE_MAX;
+	port->headroom_len = headroom_len;
 	mutex_init(&port->ops_lock);
 	skb_queue_head_init(&port->rxq);
 	init_waitqueue_head(&port->waitqueue);
@@ -698,30 +706,53 @@  static ssize_t wwan_port_fops_read(struct file *filp, char __user *buf,
 static ssize_t wwan_port_fops_write(struct file *filp, const char __user *buf,
 				    size_t count, loff_t *offp)
 {
+	struct sk_buff *skb, *head = NULL, *tail = NULL;
 	struct wwan_port *port = filp->private_data;
-	struct sk_buff *skb;
+	size_t frag_len, remain = count;
 	int ret;
 
 	ret = wwan_wait_tx(port, !!(filp->f_flags & O_NONBLOCK));
 	if (ret)
 		return ret;
 
-	skb = alloc_skb(count, GFP_KERNEL);
-	if (!skb)
-		return -ENOMEM;
+	do {
+		frag_len = min(remain, port->frag_len);
+		skb = alloc_skb(frag_len + port->headroom_len, GFP_KERNEL);
+		if (!skb) {
+			ret = -ENOMEM;
+			goto freeskb;
+		}
+		skb_reserve(skb, port->headroom_len);
+
+		if (!head) {
+			head = skb;
+		} else if (!tail) {
+			skb_shinfo(head)->frag_list = skb;
+			tail = skb;
+		} else {
+			tail->next = skb;
+			tail = skb;
+		}
 
-	if (copy_from_user(skb_put(skb, count), buf, count)) {
-		kfree_skb(skb);
-		return -EFAULT;
-	}
+		if (copy_from_user(skb_put(skb, frag_len), buf + count - remain, frag_len)) {
+			ret = -EFAULT;
+			goto freeskb;
+		}
 
-	ret = wwan_port_op_tx(port, skb, !!(filp->f_flags & O_NONBLOCK));
-	if (ret) {
-		kfree_skb(skb);
-		return ret;
-	}
+		if (skb != head) {
+			head->data_len += skb->len;
+			head->len += skb->len;
+			head->truesize += skb->truesize;
+		}
+	} while (remain -= frag_len);
+
+	ret = wwan_port_op_tx(port, head, !!(filp->f_flags & O_NONBLOCK));
+	if (!ret)
+		return count;
 
-	return count;
+freeskb:
+	kfree_skb(head);
+	return ret;
 }
 
 static __poll_t wwan_port_fops_poll(struct file *filp, poll_table *wait)
diff --git a/drivers/net/wwan/wwan_hwsim.c b/drivers/net/wwan/wwan_hwsim.c
index ff09a8cedf93..7fb54cb51628 100644
--- a/drivers/net/wwan/wwan_hwsim.c
+++ b/drivers/net/wwan/wwan_hwsim.c
@@ -205,6 +205,7 @@  static struct wwan_hwsim_port *wwan_hwsim_port_new(struct wwan_hwsim_dev *dev)
 
 	port->wwan = wwan_create_port(&dev->dev, WWAN_PORT_AT,
 				      &wwan_hwsim_port_ops,
+				      WWAN_NO_FRAGMENT, WWAN_NO_HEADROOM,
 				      port);
 	if (IS_ERR(port->wwan)) {
 		err = PTR_ERR(port->wwan);
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 1f0951be15ab..e0f0bc878bbd 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -929,7 +929,8 @@  static void wdm_wwan_init(struct wdm_device *desc)
 		return;
 	}
 
-	port = wwan_create_port(&intf->dev, desc->wwanp_type, &wdm_wwan_port_ops, desc);
+	port = wwan_create_port(&intf->dev, desc->wwanp_type, &wdm_wwan_port_ops,
+				WWAN_NO_FRAGMENT, WWAN_NO_HEADROOM, desc);
 	if (IS_ERR(port)) {
 		dev_err(&intf->dev, "%s: Unable to create WWAN port\n",
 			dev_name(intf->usb_dev));
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
index 5ce2acf444fb..adaf1f4a8652 100644
--- a/include/linux/wwan.h
+++ b/include/linux/wwan.h
@@ -62,11 +62,25 @@  struct wwan_port_ops {
 			    poll_table *wait);
 };
 
+/*
+ * Used to indicate that the WWAN core should not fragment control packages.
+ */
+#define WWAN_NO_FRAGMENT	0
+
+/*
+ * Used to indicate that the WWAN core should not reserve headroom in control packages.
+ */
+#define WWAN_NO_HEADROOM	0
+
 /**
  * wwan_create_port - Add a new WWAN port
  * @parent: Device to use as parent and shared by all WWAN ports
  * @type: WWAN port type
  * @ops: WWAN port operations
+ * @frag_len: WWAN port TX fragments length, if WWAN_NO_FRAGMENT is set,
+ *            the WWAN core don't fragment control packages.
+ * @headroom_len: WWAN port TX fragments reserved headroom length, if WWAN_NO_HEADROOM
+ *                is set, the WWAN core don't reserve headroom in control packages.
  * @drvdata: Pointer to caller driver data
  *
  * Allocate and register a new WWAN port. The port will be automatically exposed
@@ -84,6 +98,8 @@  struct wwan_port_ops {
 struct wwan_port *wwan_create_port(struct device *parent,
 				   enum wwan_port_type type,
 				   const struct wwan_port_ops *ops,
+				   size_t frag_len,
+				   unsigned int headroom_len,
 				   void *drvdata);
 
 /**