From a80509c76bf2b10dae76f3caea343ac4b85c72b4 Mon Sep 17 00:00:00 2001 From: "Mark A. Greer" Date: Tue, 23 Sep 2014 16:38:11 -0700 Subject: [PATCH] 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 ++ net/nfc/digital_dep.c | 69 +++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 66 insertions(+), 5 deletions(-) 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); diff --git a/net/nfc/digital_dep.c b/net/nfc/digital_dep.c index 35a9edf0e360..9840e858ec5b 100644 --- a/net/nfc/digital_dep.c +++ b/net/nfc/digital_dep.c @@ -17,6 +17,8 @@ #include "digital.h" +#define DIGITAL_NFC_DEP_N_RETRY_NACK 2 + #define DIGITAL_NFC_DEP_FRAME_DIR_OUT 0xD4 #define DIGITAL_NFC_DEP_FRAME_DIR_IN 0xD5 @@ -529,6 +531,38 @@ static int digital_in_send_ack(struct nfc_digital_dev *ddev, return rc; } +static int digital_in_send_nack(struct nfc_digital_dev *ddev, + struct digital_data_exch *data_exch) +{ + struct digital_dep_req_res *dep_req; + struct sk_buff *skb; + int rc; + + skb = digital_skb_alloc(ddev, 1); + if (!skb) + return -ENOMEM; + + skb_push(skb, sizeof(struct digital_dep_req_res)); + + dep_req = (struct digital_dep_req_res *)skb->data; + + dep_req->dir = DIGITAL_NFC_DEP_FRAME_DIR_OUT; + dep_req->cmd = DIGITAL_CMD_DEP_REQ; + dep_req->pfb = DIGITAL_NFC_DEP_PFB_ACK_NACK_PDU | + DIGITAL_NFC_DEP_PFB_NACK_BIT | ddev->curr_nfc_dep_pni; + + digital_skb_push_dep_sod(ddev, skb); + + ddev->skb_add_crc(skb); + + rc = digital_in_send_cmd(ddev, skb, 1500, digital_in_recv_dep_res, + data_exch); + if (rc) + kfree_skb(skb); + + return rc; +} + static int digital_in_send_rtox(struct nfc_digital_dev *ddev, struct digital_data_exch *data_exch, u8 rtox) { @@ -575,20 +609,43 @@ static void digital_in_recv_dep_res(struct nfc_digital_dev *ddev, void *arg, if (IS_ERR(resp)) { rc = PTR_ERR(resp); resp = NULL; + + if ((rc != -ETIMEDOUT) && + (ddev->nack_count++ < DIGITAL_NFC_DEP_N_RETRY_NACK)) { + rc = digital_in_send_nack(ddev, data_exch); + if (rc) + goto error; + + return; + } + + goto exit; + } + + rc = digital_skb_pull_dep_sod(ddev, resp); + if (rc) { + PROTOCOL_ERR("14.4.1.2"); goto exit; } rc = ddev->skb_check_crc(resp); if (rc) { + if ((resp->len >= 4) && + (ddev->nack_count++ < DIGITAL_NFC_DEP_N_RETRY_NACK)) { + rc = digital_in_send_nack(ddev, data_exch); + if (rc) + goto error; + + kfree_skb(resp); + + return; + } + PROTOCOL_ERR("14.4.1.6"); goto error; } - rc = digital_skb_pull_dep_sod(ddev, resp); - if (rc) { - PROTOCOL_ERR("14.4.1.2"); - goto exit; - } + ddev->nack_count = 0; if (resp->len > ddev->local_payload_max) { rc = -EMSGSIZE; @@ -721,6 +778,8 @@ int digital_in_send_dep_req(struct nfc_digital_dev *ddev, dep_req->cmd = DIGITAL_CMD_DEP_REQ; dep_req->pfb = ddev->curr_nfc_dep_pni; + ddev->nack_count = 0; + chaining_skb = ddev->chaining_skb; tmp_skb = digital_send_dep_data_prep(ddev, skb, dep_req, data_exch); -- 2.11.0