BMC/Intel-BMC/linux.git/net/nfc/digital_dep.c, branch dev

NFC: digital: Add NFC-DEP Target-side ATN Support

2014-11-28T11:40:38+00:00

When an NFC-DEP target receives an ATN PDU, its supposed to respond with a similar ATN PDU. When the Target receives an I PDU with the PNI one less than the current PNI and the last PDU sent was an ATN PDU, the Target is to resend the last non-ATN PDU that it has sent. This is described in section 14.12.3.4 of the NFC Digital Protocol Spec. The digital layer's NFC-DEP code doesn't implement this so add that support. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Add NFC-DEP Initiator-side ATN Support

2014-11-28T11:39:55+00:00

When an NFC-DEP Initiator times out when waiting for a DEP_RES from the Target, its supposed to send an ATN to the Target. The Target should respond to the ATN with a similar ATN PDU and the Initiator can then resend the last non-ATN PDU that it sent. No more than 'N(retry,atn)' are to be send where 2 <= 'N(retry,atn)' <= 5. If the Initiator had just sent a NACK PDU when the timeout occurred, it is to continue sending NACKs until 'N(retry,nack)' NACKs have been send. This is described in section 14.12.5.6 of the NFC-DEP Digital Protocol Spec. The digital layer's NFC-DEP code doesn't implement this so add that support. The value chosen for 'N(retry,atn)' is 2. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Add NFC-DEP Target-side NACK Support

2014-11-28T11:39:47+00:00

When an NFC-DEP Target receives a NACK PDU with a PNI equal to 1 less than the current PNI, it is supposed to re-send the last PDU. This is implied in section 14.12.5.4 of the NFC Digital Protocol Spec. The digital layer's NFC-DEP code doesn't implement Target-side NACK handing so add it. The last PDU that was sent is saved in the 'nfc_digital_dev' structure's 'saved_skb' member. The skb will have an additional reference taken to ensure that the skb isn't freed when the driver performs a kfree_skb() on the skb. The length of the skb/PDU is also saved so the length can be restored when re-sending the PDU in the skb (the driver will perform an skb_pull() so an skb_push() needs to be done to restore the skb's data pointer/length). Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Add NFC-DEP Initiator-side NACK Support

2014-11-28T11:39:33+00:00

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

NFC: digital: Add NFC-DEP Receive Chaining Support

2014-11-28T11:39:21+00:00

When the peer in an NFC-DEP exchange has a packet to send that is larger than the local maximum payload, it sets the 'MI' bit in the 'I' PDU. This indicates that NFC-DEP chaining is to occur. When such a PDU is received, the local side responds with an 'ACK' PDU and this continues until the peer sends an 'I' PDU with the 'MI' bit cleared. This indicates that the chaining sequence is complete and the entire packet has been transferred. Receiving chained PDUs is currently not supported by the digital layer so add that support. When a chaining sequence is initiated by the peer, the digital layer will allocate an skb large enough to hold 8 maximum sized frame payloads. The maximum payload can range from 64 to 254 bytes so 8 * 254 = 2032 seems like a reasonable compromise between potentially wasting memory and constantly reallocating new, larger skbs. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Add NFC-DEP Send Chaining Support

2014-11-28T11:39:10+00:00

When the NFC-DEP code is given a packet to send that is larger than the peer's maximum payload, its supposed to set the 'MI' bit in the 'I' PDU's Protocol Frame Byte (PFB). Setting this bit indicates that NFC-DEP chaining is to occur. When NFC-DEP chaining is progress, sender 'I' PDUs are acknowledged with 'ACK' PDUs until the last 'I' PDU in the chain (which has the 'MI' bit cleared) is responded to with a normal 'I' PDU. This can occur while in Initiator mode or in Target mode. Sender NFC-DEP chaining is currently not implemented in the digital layer so add that support. Unfortunately, since sending a frame may require writing the CRC to the end of the data, the relevant data part of the original skb must be copied for each intermediate frame. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Implement NFC-DEP max payload lengths

2014-11-28T11:38:59+00:00

The maximum payload for NFC-DEP exchanges (i.e., the number of bytes between SoD and EoD) is negotiated using the ATR_REQ, ATR_RES, and PSL_REQ commands. The valid maximum lengths are 64, 128, 192, and 254 bytes. Currently, NFC-DEP code assumes that both sides are always using 254 byte maximums and ignores attempts by the peer to change it. Instead, implement the negotiation code, enforce the local maximum when receiving data from the peer, and don't send payloads that exceed the remote's maximum. The default local maximum is 254 bytes. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Enforce NFC-DEP PNI sequencing

2014-11-28T11:38:47+00:00

NFC-DEP DEP_REQ and DEP_RES exchanges using 'I' and 'ACK/NACK' PDUs have a sequence number called the Packet Number Information (PNI). The PNI is incremented (modulo 4) after every DEP_REQ/ DEP_RES pair and should be verified by the digital layer code. That verification isn't always done, though, so add code to make sure that it is done. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Ensure no NAD byte in DEP_REQ and DEP_RES frames

2014-11-28T11:38:36+00:00

According to chapter 14 of the NFC-DEP Digital Protocol Spec., the NAD byte should never be present in DEP_REQ or DEP_RES frames. However, this is not enforced so add that enforcement code. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz

NFC: digital: Add Target-mode NFC-DEP DID Support

2014-11-28T11:38:24+00:00

When in Target mode, the Initiator specifies whether subsequent DEP_REQ and DEP_RES frames will include a DID byte by the value passed in the ATR_REQ. If the DID value in the ATR_REQ is '0' then no DID byte will be included. If the DID value is between '1' and '14' then a DID byte containing the same value must be included in subsequent DEP_REQ and DEP_RES frames. Any other DID value is invalid. This is specified in sections 14.8.1.2 and 14.8.2.2 of the NFC Digital Protocol Spec. Checking the DID value (if it should be there at all), is not currently supported by the digital layer's NFC-DEP code. Add this support by remembering the DID value in the ATR_REQ, checking the DID value of received DEP_REQ frames (if it should be there at all), and including the remembered DID value in DEP_RES frames when appropriate. Reviewed-by: Thierry Escande Tested-by: Thierry Escande Signed-off-by: Mark A. Greer Signed-off-by: Samuel Ortiz