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authorMark A. Greer <mgreer@animalcreek.com>2014-09-24 03:38:11 +0400
committerSamuel Ortiz <sameo@linux.intel.com>2014-11-28 14:39:33 +0300
commita80509c76bf2b10dae76f3caea343ac4b85c72b4 (patch)
tree924f14ca602ddecd0bb5b81e7201628882b07375
parentc12715ab3f0122971f75731b9c2f5b35836165cb (diff)
downloadlinux-a80509c76bf2b10dae76f3caea343ac4b85c72b4.tar.xz
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 <thierry.escande@linux.intel.com> Tested-by: Thierry Escande <thierry.escande@linux.intel.com> Signed-off-by: Mark A. Greer <mgreer@animalcreek.com> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
-rw-r--r--include/net/nfc/digital.h2
-rw-r--r--net/nfc/digital_dep.c69
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);