NFC: SHDLC implementation

Most NFC HCI chipsets actually use a simplified HDLC link layer to
carry HCI payloads.
This implementation registers itself as an HCI device on behalf of the
NFC driver.
Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/nfc/shdlc.h

+/*
+ * Copyright (C) 2012  Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the
+ * Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __NFC_SHDLC_H
+#define __NFC_SHDLC_H
+
+struct nfc_shdlc;
+
+struct nfc_shdlc_ops {
+	int (*open) (struct nfc_shdlc *shdlc);
+	void (*close) (struct nfc_shdlc *shdlc);
+	int (*hci_ready) (struct nfc_shdlc *shdlc);
+	int (*xmit) (struct nfc_shdlc *shdlc, struct sk_buff *skb);
+	int (*start_poll) (struct nfc_shdlc *shdlc, u32 protocols);
+	int (*target_from_gate) (struct nfc_shdlc *shdlc, u8 gate,
+				 struct nfc_target *target);
+	int (*complete_target_discovered) (struct nfc_shdlc *shdlc, u8 gate,
+					   struct nfc_target *target);
+	int (*data_exchange) (struct nfc_shdlc *shdlc,
+			      struct nfc_target *target,
+			      struct sk_buff *skb, struct sk_buff **res_skb);
+};
+
+enum shdlc_state {
+	SHDLC_DISCONNECTED = 0,
+	SHDLC_CONNECTING = 1,
+	SHDLC_NEGOCIATING = 2,
+	SHDLC_CONNECTED = 3
+};
+
+struct nfc_shdlc {
+	struct mutex state_mutex;
+	enum shdlc_state state;
+	int hard_fault;
+
+	struct nfc_hci_dev *hdev;
+
+	wait_queue_head_t *connect_wq;
+	int connect_tries;
+	int connect_result;
+	struct timer_list connect_timer;/* aka T3 in spec 10.6.1 */
+
+	u8 w;				/* window size */
+	bool srej_support;
+
+	struct timer_list t1_timer;	/* send ack timeout */
+	bool t1_active;
+
+	struct timer_list t2_timer;	/* guard/retransmit timeout */
+	bool t2_active;
+
+	int ns;				/* next seq num for send */
+	int nr;				/* next expected seq num for receive */
+	int dnr;			/* oldest sent unacked seq num */
+
+	struct sk_buff_head rcv_q;
+
+	struct sk_buff_head send_q;
+	bool rnr;			/* other side is not ready to receive */
+
+	struct sk_buff_head ack_pending_q;
+
+	struct workqueue_struct *sm_wq;
+	struct work_struct sm_work;
+
+	struct nfc_shdlc_ops *ops;
+
+	int client_headroom;
+	int client_tailroom;
+
+	void *clientdata;
+};
+
+void nfc_shdlc_recv_frame(struct nfc_shdlc *shdlc, struct sk_buff *skb);
+
+struct nfc_shdlc *nfc_shdlc_allocate(struct nfc_shdlc_ops *ops,
+				     struct nfc_hci_init_data *init_data,
+				     u32 protocols,
+				     int tx_headroom, int tx_tailroom,
+				     int max_link_payload, const char *devname);
+
+void nfc_shdlc_free(struct nfc_shdlc *shdlc);
+
+void nfc_shdlc_set_clientdata(struct nfc_shdlc *shdlc, void *clientdata);
+void *nfc_shdlc_get_clientdata(struct nfc_shdlc *shdlc);
+struct nfc_hci_dev *nfc_shdlc_get_hci_dev(struct nfc_shdlc *shdlc);
+
+#endif /* __NFC_SHDLC_H */

net/nfc/hci/Kconfig

@@ -6,3 +6,11 @@ config NFC_HCI
 	 Say Y here if you want to build support for a kernel NFC HCI
 	 implementation. This is mostly needed for devices that only process
 	 HCI frames, like for example the NXP pn544.
+
+config NFC_SHDLC
+	depends on NFC_HCI
+	bool "SHDLC link layer for HCI based NFC drivers"
+	default n
+	---help---
+	  Say yes if you use an NFC HCI driver that requires SHDLC link layer.
+	  If unsure, say N here.

net/nfc/hci/Makefile

@@ -5,3 +5,4 @@
 obj-$(CONFIG_NFC_HCI) += hci.o
 
 hci-y			:= core.o hcp.o command.o
+hci-$(CONFIG_NFC_SHDLC)	+= shdlc.o