[RFC] Bluetooth: mgmt: Introduce mgmt_alloc_skb and mgmt_send_event_skb

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

This introduces mgmt_alloc_skb and mgmt_send_event_skb which are
convenient when building MGMT events that have variable length as the
likes of skb_put_data can be used to insert portion directly on the skb
instead of having to first build an intermediate buffer just to be
copied over the skb.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/mgmt_util.c | 54 +++++++++++++++++++++++++++------------
 net/bluetooth/mgmt_util.h |  3 +++
 2 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/net/bluetooth/mgmt_util.c b/net/bluetooth/mgmt_util.c
index 83875f2a0604..4774e993d774 100644
--- a/net/bluetooth/mgmt_util.c
+++ b/net/bluetooth/mgmt_util.c
@@ -56,40 +56,60 @@ static struct sk_buff *create_monitor_ctrl_event(__le16 index, u32 cookie,
 	return skb;
 }
 
-int mgmt_send_event(u16 event, struct hci_dev *hdev, unsigned short channel,
-		    void *data, u16 data_len, int flag, struct sock *skip_sk)
+struct sk_buff *mgmt_alloc_skb(unsigned int size)
 {
 	struct sk_buff *skb;
+
+	skb = alloc_skb(sizeof(struct mgmt_hdr) + size, GFP_KERNEL);
+	if (skb)
+		skb_reserve(skb, sizeof(struct mgmt_hdr));
+
+	return skb;
+}
+
+int mgmt_send_event_skb(u16 event, struct hci_dev *hdev, unsigned short channel,
+			struct sk_buff *skb, int flag, struct sock *skip_sk)
+{
 	struct mgmt_hdr *hdr;
+	int len = skb->len;
 
-	skb = alloc_skb(sizeof(*hdr) + data_len, GFP_KERNEL);
-	if (!skb)
-		return -ENOMEM;
+	/* Time stamp */
+	__net_timestamp(skb);
 
-	hdr = skb_put(skb, sizeof(*hdr));
+	/* Send just the data, without headers, to the monitor */
+	if (channel == HCI_CHANNEL_CONTROL)
+		hci_send_monitor_ctrl_event(hdev, event, skb->data, skb->len,
+					    skb_get_ktime(skb), flag, skip_sk);
+
+	hdr = skb_push(skb, sizeof(*hdr));
 	hdr->opcode = cpu_to_le16(event);
 	if (hdev)
 		hdr->index = cpu_to_le16(hdev->id);
 	else
 		hdr->index = cpu_to_le16(MGMT_INDEX_NONE);
-	hdr->len = cpu_to_le16(data_len);
-
-	if (data)
-		skb_put_data(skb, data, data_len);
-
-	/* Time stamp */
-	__net_timestamp(skb);
+	hdr->len = cpu_to_le16(len);
 
 	hci_send_to_channel(channel, skb, flag, skip_sk);
 
-	if (channel == HCI_CHANNEL_CONTROL)
-		hci_send_monitor_ctrl_event(hdev, event, data, data_len,
-					    skb_get_ktime(skb), flag, skip_sk);
-
 	kfree_skb(skb);
 	return 0;
 }
 
+int mgmt_send_event(u16 event, struct hci_dev *hdev, unsigned short channel,
+		    void *data, u16 data_len, int flag, struct sock *skip_sk)
+{
+	struct sk_buff *skb;
+
+	skb = mgmt_alloc_skb(data_len);
+	if (!skb)
+		return -ENOMEM;
+
+	if (data)
+		skb_put_data(skb, data, data_len);
+
+	return mgmt_send_event_skb(event, hdev, channel, skb, flag, skip_sk);
+}
+
 int mgmt_cmd_status(struct sock *sk, u16 index, u16 cmd, u8 status)
 {
 	struct sk_buff *skb, *mskb;
diff --git a/net/bluetooth/mgmt_util.h b/net/bluetooth/mgmt_util.h
index 63b965eaaaac..9f8692d4ce90 100644
--- a/net/bluetooth/mgmt_util.h
+++ b/net/bluetooth/mgmt_util.h
@@ -32,6 +32,9 @@ struct mgmt_pending_cmd {
 	int (*cmd_complete)(struct mgmt_pending_cmd *cmd, u8 status);
 };
 
+struct sk_buff *mgmt_alloc_skb(unsigned int size);
+int mgmt_send_event_skb(u16 event, struct hci_dev *hdev, unsigned short channel,
+			struct sk_buff *skb, int flag, struct sock *skip_sk);
 int mgmt_send_event(u16 event, struct hci_dev *hdev, unsigned short channel,
 		    void *data, u16 data_len, int flag, struct sock *skip_sk);
 int mgmt_cmd_status(struct sock *sk, u16 index, u16 cmd, u8 status);
-- 
2.33.1