NFC: netlink: Add new netlink command NFC_CMD_ACTIVATE_TARGET

Some tag might get deactivated after some read or write tentative.
This may happen for example with Mifare Ultralight C tag when trying
to read the last 4 blocks (starting block 0x2c) configured as write
only.
NFC_CMD_ACTIVATE_TARGET will try to reselect the tag in order to
detect if it got remove from the field or if it is still present.
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/uapi/linux/nfc.h

@@ -116,6 +116,7 @@ enum nfc_commands {
 	NFC_EVENT_SE_TRANSACTION,
 	NFC_CMD_GET_SE,
 	NFC_CMD_SE_IO,
+	NFC_CMD_ACTIVATE_TARGET,
 /* private: internal use only */
 	__NFC_CMD_AFTER_LAST
 };

net/nfc/netlink.c

@@ -810,6 +810,31 @@ static int nfc_genl_stop_poll(struct sk_buff *skb, struct genl_info *info)
 	return rc;
 }
 
+static int nfc_genl_activate_target(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nfc_dev *dev;
+	u32 device_idx, target_idx, protocol;
+	int rc;
+
+	if (!info->attrs[NFC_ATTR_DEVICE_INDEX])
+		return -EINVAL;
+
+	device_idx = nla_get_u32(info->attrs[NFC_ATTR_DEVICE_INDEX]);
+
+	dev = nfc_get_device(device_idx);
+	if (!dev)
+		return -ENODEV;
+
+	target_idx = nla_get_u32(info->attrs[NFC_ATTR_TARGET_INDEX]);
+	protocol = nla_get_u32(info->attrs[NFC_ATTR_PROTOCOLS]);
+
+	nfc_deactivate_target(dev, target_idx);
+	rc = nfc_activate_target(dev, target_idx, protocol);
+
+	nfc_put_device(dev);
+	return 0;
+}
+
 static int nfc_genl_dep_link_up(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nfc_dev *dev;
@@ -1455,6 +1480,11 @@ static const struct genl_ops nfc_genl_ops[] = {
 		.doit = nfc_genl_se_io,
 		.policy = nfc_genl_policy,
 	},
+	{
+		.cmd = NFC_CMD_ACTIVATE_TARGET,
+		.doit = nfc_genl_activate_target,
+		.policy = nfc_genl_policy,
+	},
 };