From a80509c76bf2b10dae76f3caea343ac4b85c72b4 Mon Sep 17 00:00:00 2001 From: "Mark A. Greer" Date: Tue, 23 Sep 2014 16:38:11 -0700 Subject: NFC: digital: Add NFC-DEP Initiator-side NACK Support When an NFC-DEP Initiator receives a frame with an incorrect CRC or with a parity error, and the frame is at least 4 bytes long, its supposed to send a NACK to the Target. The Initiator can send up to 'N(retry,nack)' consecutive NACKs where 2 <= 'N(retry,nack)' <= 5. When the limit is exceeded, a PROTOCOL EXCEPTION is raised. Any other type of transmission error is to be ignored and the Initiator should continue waiting for a new frame. This is described in section 14.12.5.4 of the NFC Digital Protocol Spec. The digital layer's NFC-DEP code doesn't implement any of this so add it. This support diverges from the spec in two significant ways: a) NACKs will be sent for ANY error reported by the driver except a timeout. This is done because there is currently no way for the digital layer to distinguish a CRC or parity error from any other type of error reported by the driver. b) All other errors will cause a PROTOCOL EXCEPTION even frames with CRC errors that are less than 4 bytes. The value chosen for 'N(retry,nack)' is 2. Targets do not send NACK PDUs. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz --- include/net/nfc/digital.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/net/nfc/digital.h') diff --git a/include/net/nfc/digital.h b/include/net/nfc/digital.h index 2fdff00e06cd..2fd498cdb818 100644 --- a/include/net/nfc/digital.h +++ b/include/net/nfc/digital.h @@ -233,6 +233,8 @@ struct nfc_digital_dev { struct sk_buff *chaining_skb; struct digital_data_exch *data_exch; + int nack_count; + u16 target_fsc; int (*skb_check_crc)(struct sk_buff *skb); -- cgit v1.2.3-59-g8ed1b