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0bd606b31d
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>