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>
diff --git a/net/nfc/digital_dep.c b/net/nfc/digital_dep.c
index 35a9edf..9840e85 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 @@
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)
{
@@ -575,13 +609,17 @@
if (IS_ERR(resp)) {
rc = PTR_ERR(resp);
resp = NULL;
- goto exit;
- }
- rc = ddev->skb_check_crc(resp);
- if (rc) {
- PROTOCOL_ERR("14.4.1.6");
- goto error;
+ 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);
@@ -590,6 +628,25 @@
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;
+ }
+
+ ddev->nack_count = 0;
+
if (resp->len > ddev->local_payload_max) {
rc = -EMSGSIZE;
goto exit;
@@ -721,6 +778,8 @@
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);