NFC: microread: Add MEI physical layer

On some peculiar worlds, microreads are found hidden behind MEIs and needs
to be accessed through the ME bus.

Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/nfc/microread/Kconfig

···
 
 	  If you choose to build a module, it'll be called microread_i2c.
 	  Say N if unsure.
+
+config NFC_MICROREAD_MEI
+	tristate "NFC Microread MEI support"
+	depends on NFC_MICROREAD && INTEL_MEI_BUS_NFC
+	---help---
+	  This module adds support for the mei interface of adapters using
+	  Inside microread chipsets.  Select this if your microread chipset
+	  is handled by Intel's Management Engine Interface on your platform.
+
+	  If you choose to build a module, it'll be called microread_mei.
+	  Say N if unsure.

drivers/nfc/microread/Makefile

···
 #
 
 microread_i2c-objs  = i2c.o
+microread_mei-objs  = mei.o
 
 obj-$(CONFIG_NFC_MICROREAD)     += microread.o
 obj-$(CONFIG_NFC_MICROREAD_I2C) += microread_i2c.o
+obj-$(CONFIG_NFC_MICROREAD_MEI) += microread_mei.o

drivers/nfc/microread/mei.c

···
+/*
+ * HCI based Driver for Inside Secure microread NFC Chip
+ *
+ * Copyright (C) 2013  Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/gpio.h>
+#include <linux/mei_bus.h>
+
+#include <linux/nfc.h>
+#include <net/nfc/hci.h>
+#include <net/nfc/llc.h>
+
+#include "microread.h"
+
+#define MICROREAD_DRIVER_NAME "microread"
+
+#define MICROREAD_UUID UUID_LE(0x0bb17a78, 0x2a8e, 0x4c50, 0x94, \
+			       0xd4, 0x50, 0x26, 0x67, 0x23, 0x77, 0x5c)
+
+struct mei_nfc_hdr {
+	u8 cmd;
+	u8 status;
+	u16 req_id;
+	u32 reserved;
+	u16 data_size;
+} __attribute__((packed));
+
+#define MEI_NFC_HEADER_SIZE 10
+#define MEI_NFC_MAX_HCI_PAYLOAD 300
+#define MEI_NFC_MAX_READ (MEI_NFC_HEADER_SIZE + MEI_NFC_MAX_HCI_PAYLOAD)
+
+struct microread_mei_phy {
+	struct mei_bus_client *client;
+	struct nfc_hci_dev *hdev;
+
+	int powered;
+
+	int hard_fault;		/*
+				 * < 0 if hardware error occured (e.g. i2c err)
+				 * and prevents normal operation.
+				 */
+};
+
+#define MEI_DUMP_SKB_IN(info, skb)					\
+do {								\
+	pr_debug("%s:\n", info);				\
+	print_hex_dump(KERN_DEBUG, "mei in : ", DUMP_PREFIX_OFFSET,	\
+		       16, 1, (skb)->data, (skb)->len, 0);	\
+} while (0)
+
+#define MEI_DUMP_SKB_OUT(info, skb)					\
+do {								\
+	pr_debug("%s:\n", info);				\
+	print_hex_dump(KERN_DEBUG, "mei out: ", DUMP_PREFIX_OFFSET,	\
+		       16, 1, (skb)->data, (skb)->len, 0);	\
+} while (0)
+
+static int microread_mei_enable(void *phy_id)
+{
+	struct microread_mei_phy *phy = phy_id;
+
+	pr_info(DRIVER_DESC ": %s\n", __func__);
+
+	phy->powered = 1;
+
+	return 0;
+}
+
+static void microread_mei_disable(void *phy_id)
+{
+	struct microread_mei_phy *phy = phy_id;
+
+	pr_info(DRIVER_DESC ": %s\n", __func__);
+
+	phy->powered = 0;
+}
+
+/*
+ * Writing a frame must not return the number of written bytes.
+ * It must return either zero for success, or <0 for error.
+ * In addition, it must not alter the skb
+ */
+static int microread_mei_write(void *phy_id, struct sk_buff *skb)
+{
+	struct microread_mei_phy *phy = phy_id;
+	int r;
+
+	MEI_DUMP_SKB_OUT("mei frame sent", skb);
+
+	r = mei_bus_send(phy->client, skb->data, skb->len);
+	if (r > 0)
+		r = 0;
+
+	return r;
+}
+
+static void microread_event_cb(struct mei_bus_client *client, u32 events,
+			       void *context)
+{
+	struct microread_mei_phy *phy = context;
+
+	if (phy->hard_fault != 0)
+		return;
+
+	if (events & BIT(MEI_BUS_EVENT_RX)) {
+		struct sk_buff *skb;
+		int reply_size;
+
+		skb = alloc_skb(MEI_NFC_MAX_READ, GFP_KERNEL);
+		if (!skb)
+			return;
+
+		reply_size = mei_bus_recv(client, skb->data, MEI_NFC_MAX_READ);
+		if (reply_size < MEI_NFC_HEADER_SIZE) {
+			kfree(skb);
+			return;
+		}
+
+		skb_put(skb, reply_size);
+		skb_pull(skb, MEI_NFC_HEADER_SIZE);
+
+		MEI_DUMP_SKB_IN("mei frame read", skb);
+
+		nfc_hci_recv_frame(phy->hdev, skb);
+	}
+}
+
+static struct nfc_phy_ops mei_phy_ops = {
+	.write = microread_mei_write,
+	.enable = microread_mei_enable,
+	.disable = microread_mei_disable,
+};
+
+static int microread_mei_probe(struct mei_bus_client *client)
+{
+	struct microread_mei_phy *phy;
+	int r;
+
+	pr_info("Probing NFC microread\n");
+
+	phy = kzalloc(sizeof(struct microread_mei_phy), GFP_KERNEL);
+	if (!phy) {
+		pr_err("Cannot allocate memory for microread mei phy.\n");
+		return -ENOMEM;
+	}
+
+	phy->client = client;
+	mei_bus_set_clientdata(client, phy);
+
+	r = mei_bus_register_event_cb(client, microread_event_cb, phy);
+	if (r) {
+		pr_err(MICROREAD_DRIVER_NAME ": event cb registration failed\n");
+		goto err_out;
+	}
+
+	r = microread_probe(phy, &mei_phy_ops, LLC_NOP_NAME,
+			    MEI_NFC_HEADER_SIZE, 0, MEI_NFC_MAX_HCI_PAYLOAD,
+			    &phy->hdev);
+	if (r < 0)
+		goto err_out;
+
+	return 0;
+
+err_out:
+	kfree(phy);
+
+	return r;
+}
+
+static int microread_mei_remove(struct mei_bus_client *client)
+{
+	struct microread_mei_phy *phy = mei_bus_get_clientdata(client);
+
+	pr_info("Removing microread\n");
+
+	microread_remove(phy->hdev);
+
+	if (phy->powered)
+		microread_mei_disable(phy);
+
+	kfree(phy);
+
+	return 0;
+}
+
+static struct mei_bus_driver microread_driver = {
+	.driver = {
+		   .name = MICROREAD_DRIVER_NAME,
+		  },
+	.id = {
+		.name = MICROREAD_DRIVER_NAME,
+		.uuid = MICROREAD_UUID,
+	},
+
+	.probe = microread_mei_probe,
+	.remove = microread_mei_remove,
+};
+
+static int microread_mei_init(void)
+{
+	int r;
+
+	pr_debug(DRIVER_DESC ": %s\n", __func__);
+
+	r = mei_driver_register(&microread_driver);
+	if (r) {
+		pr_err(MICROREAD_DRIVER_NAME ": driver registration failed\n");
+		return r;
+	}
+
+	return 0;
+}
+
+static void microread_mei_exit(void)
+{
+	mei_driver_unregister(&microread_driver);
+}
+
+module_init(microread_mei_init);
+module_exit(microread_mei_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION(DRIVER_DESC);