Bluetooth: hci_event: Introduce handle_ev_vendor() for HCI_EV_VENDOR

Introduce the hook to solve issues below:

msft_vendor_evt(), the current handler for all VSEs, is unsuitable
since:
- many VSEs are not MSFT ones;
- it always corrupts the non-MSFT VSEs by calling skb_pull_data()
  once the MSFT extension is enabled.

Several issues are caused by many transport drivers pre-processing
VSEs in their RX path, often an IRQ-disabled atomic context. Take
the two typical cases below as examples:

Case 1:
  // no btmon log, no way to reach userspace
  Step 1: handle and free @original_skb directly

Case 2:
  // hurts performance and consumes GFP_ATOMIC memory
  Step 1: cloned_skb = skb_clone(original_skb, GFP_ATOMIC);
  // the VSE is handled here
  Step 2: handle and free @cloned_skb
  Step 3: hci_recv_frame(hdev, original_skb);
  // already handled, but re-enters the stack's event-handling path
  Step 4: hci_event_packet(hdev, original_skb);

Fix by introducing the hook with usage:
1) the transport driver registers the hook for VSEs of interest;
2) the stack calls it in process context, handling the VSE like any
   other event:
   - if interested, handle the VSE - no need to free it - and
     return true;
   - otherwise return false.

Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 6ff47f9bf758..e07418a5adce 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -646,6 +646,8 @@ struct hci_dev {
 	int (*setup)(struct hci_dev *hdev);
 	int (*shutdown)(struct hci_dev *hdev);
 	int (*send)(struct hci_dev *hdev, struct sk_buff *skb);
+	/* Handle HCI_EV_VENDOR; return true if handled, false otherwise */
+	bool (*handle_ev_vendor)(struct hci_dev *hdev, struct sk_buff *skb);
 	void (*notify)(struct hci_dev *hdev, unsigned int evt);
 	void (*hw_error)(struct hci_dev *hdev, u8 code);
 	int (*post_init)(struct hci_dev *hdev);