i2c: New bus driver for the TAOS evaluation modules

This is a new I2C bus driver for the TAOS evaluation modules. Developped
and tested on the TAOS TSL2550 EVM.
Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/i2c/busses/i2c-taos-evm

+Kernel driver i2c-taos-evm
+
+Author: Jean Delvare <khali@linux-fr.org>
+
+This is a driver for the evaluation modules for TAOS I2C/SMBus chips.
+The modules include an SMBus master with limited capabilities, which can
+be controlled over the serial port. Virtually all evaluation modules
+are supported, but a few lines of code need to be added for each new
+module to instantiate the right I2C chip on the bus. Obviously, a driver
+for the chip in question is also needed.
+
+Currently supported devices are:
+
+* TAOS TSL2550 EVM
+
+For addtional information on TAOS products, please see
+  http://www.taosinc.com/
+
+
+Using this driver
+-----------------
+
+In order to use this driver, you'll need the serport driver, and the
+inputattach tool, which is part of the input-utils package. The following
+commands will tell the kernel that you have a TAOS EVM on the first
+serial port:
+
+# modprobe serport
+# inputattach --taos-evm /dev/ttyS0
+
+
+Technical details
+-----------------
+
+Only 4 SMBus transaction types are supported by the TAOS evaluation
+modules:
+* Receive Byte
+* Send Byte
+* Read Byte
+* Write Byte
+
+The communication protocol is text-based and pretty simple. It is
+described in a PDF document on the CD which comes with the evaluation
+module. The communication is rather slow, because the serial port has
+to operate at 1200 bps. However, I don't think this is a big concern in
+practice, as these modules are meant for evaluation and testing only.

drivers/i2c/busses/Kconfig

@@ -513,6 +513,22 @@ config I2C_SIS96X
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-sis96x.
 
+config I2C_TAOS_EVM
+	tristate "TAOS evaluation module"
+	depends on EXPERIMENTAL
+	select SERIO
+	select SERIO_SERPORT
+	default n
+	help
+	  This supports TAOS evaluation modules on serial port. In order to
+	  use this driver, you will need the inputattach tool, which is part
+	  of the input-utils package.
+
+	  If unsure, say N.
+
+	  This support is also available as a module.  If so, the module
+	  will be called i2c-taos-evm.
+
 config I2C_STUB
 	tristate "I2C/SMBus Test Stub"
 	depends on EXPERIMENTAL && m

drivers/i2c/busses/Makefile

@@ -44,6 +44,7 @@ obj-$(CONFIG_I2C_SIS5595)	+= i2c-sis5595.o
 obj-$(CONFIG_I2C_SIS630)	+= i2c-sis630.o
 obj-$(CONFIG_I2C_SIS96X)	+= i2c-sis96x.o
 obj-$(CONFIG_I2C_STUB)		+= i2c-stub.o
+obj-$(CONFIG_I2C_TAOS_EVM)	+= i2c-taos-evm.o
 obj-$(CONFIG_I2C_TINY_USB)	+= i2c-tiny-usb.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
 obj-$(CONFIG_I2C_ACORN)		+= i2c-acorn.o

drivers/i2c/busses/i2c-taos-evm.c

+/*
+ * Driver for the TAOS evaluation modules
+ * These devices include an I2C master which can be controlled over the
+ * serial port.
+ *
+ * Copyright (C) 2007 Jean Delvare <khali@linux-fr.org>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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/delay.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+
+#define TAOS_BUFFER_SIZE	63
+
+#define TAOS_STATE_INIT		0
+#define TAOS_STATE_IDLE		1
+#define TAOS_STATE_SEND		2
+#define TAOS_STATE_RECV		3
+
+#define TAOS_CMD_RESET		0x12
+
+static DECLARE_WAIT_QUEUE_HEAD(wq);
+
+struct taos_data {
+	struct i2c_adapter adapter;
+	struct i2c_client *client;
+	int state;
+	u8 addr;		/* last used address */
+	unsigned char buffer[TAOS_BUFFER_SIZE];
+	unsigned int pos;	/* position inside the buffer */
+};
+
+/* TAOS TSL2550 EVM */
+static struct i2c_board_info tsl2550_info = {
+	I2C_BOARD_INFO("tsl2550", 0x39),
+	.type	= "tsl2550",
+};
+
+/* Instantiate i2c devices based on the adapter name */
+static struct i2c_client *taos_instantiate_device(struct i2c_adapter *adapter)
+{
+	if (!strncmp(adapter->name, "TAOS TSL2550 EVM", 16)) {
+		dev_info(&adapter->dev, "Instantiating device %s at 0x%02x\n",
+			tsl2550_info.driver_name, tsl2550_info.addr);
+		return i2c_new_device(adapter, &tsl2550_info);
+	}
+
+	return NULL;
+}
+
+static int taos_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
+			   unsigned short flags, char read_write, u8 command,
+			   int size, union i2c_smbus_data *data)
+{
+	struct serio *serio = adapter->algo_data;
+	struct taos_data *taos = serio_get_drvdata(serio);
+	char *p;
+
+	/* Encode our transaction. "@" is for the device address, "$" for the
+	   SMBus command and "#" for the data. */
+	p = taos->buffer;
+
+	/* The device remembers the last used address, no need to send it
+	   again if it's the same */
+	if (addr != taos->addr)
+		p += sprintf(p, "@%02X", addr);
+
+	switch (size) {
+	case I2C_SMBUS_BYTE:
+		if (read_write == I2C_SMBUS_WRITE)
+			sprintf(p, "$#%02X", command);
+		else
+			sprintf(p, "$");
+		break;
+	case I2C_SMBUS_BYTE_DATA:
+		if (read_write == I2C_SMBUS_WRITE)
+			sprintf(p, "$%02X#%02X", command, data->byte);
+		else
+			sprintf(p, "$%02X", command);
+		break;
+	default:
+		dev_dbg(&adapter->dev, "Unsupported transaction size %d\n",
+			size);
+		return -EINVAL;
+	}
+
+	/* Send the transaction to the TAOS EVM */
+	dev_dbg(&adapter->dev, "Command buffer: %s\n", taos->buffer);
+	taos->pos = 0;
+	taos->state = TAOS_STATE_SEND;
+	serio_write(serio, taos->buffer[0]);
+	wait_event_interruptible_timeout(wq, taos->state == TAOS_STATE_IDLE,
+					 msecs_to_jiffies(250));
+	if (taos->state != TAOS_STATE_IDLE) {
+		dev_err(&adapter->dev, "Transaction failed "
+			"(state=%d, pos=%d)\n", taos->state, taos->pos);
+		taos->addr = 0;
+		return -EIO;
+	}
+	taos->addr = addr;
+
+	/* Start the transaction and read the answer */
+	taos->pos = 0;
+	taos->state = TAOS_STATE_RECV;
+	serio_write(serio, read_write == I2C_SMBUS_WRITE ? '>' : '<');
+	wait_event_interruptible_timeout(wq, taos->state == TAOS_STATE_IDLE,
+					 msecs_to_jiffies(150));
+	if (taos->state != TAOS_STATE_IDLE
+	 || taos->pos != 6) {
+		dev_err(&adapter->dev, "Transaction timeout (pos=%d)\n",
+			taos->pos);
+		return -EIO;
+	}
+	dev_dbg(&adapter->dev, "Answer buffer: %s\n", taos->buffer);
+
+	/* Interpret the returned string */
+	p = taos->buffer + 2;
+	p[3] = '\0';
+	if (!strcmp(p, "NAK"))
+		return -ENODEV;
+
+	if (read_write == I2C_SMBUS_WRITE) {
+		if (!strcmp(p, "ACK"))
+			return 0;
+	} else {
+		if (p[0] == 'x') {
+			data->byte = simple_strtol(p + 1, NULL, 16);
+			return 0;
+		}
+	}
+
+	return -EIO;
+}
+
+static u32 taos_smbus_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_BYTE_DATA;
+}
+
+static const struct i2c_algorithm taos_algorithm = {
+	.smbus_xfer	= taos_smbus_xfer,
+	.functionality	= taos_smbus_func,
+};
+
+static irqreturn_t taos_interrupt(struct serio *serio, unsigned char data,
+				  unsigned int flags)
+{
+	struct taos_data *taos = serio_get_drvdata(serio);
+
+	switch (taos->state) {
+	case TAOS_STATE_INIT:
+		taos->buffer[taos->pos++] = data;
+		if (data == ':'
+		 || taos->pos == TAOS_BUFFER_SIZE - 1) {
+			taos->buffer[taos->pos] = '\0';
+			taos->state = TAOS_STATE_IDLE;
+			wake_up_interruptible(&wq);
+		}
+		break;
+	case TAOS_STATE_SEND:
+		if (taos->buffer[++taos->pos])
+			serio_write(serio, taos->buffer[taos->pos]);
+		else {
+			taos->state = TAOS_STATE_IDLE;
+			wake_up_interruptible(&wq);
+		}
+		break;
+	case TAOS_STATE_RECV:
+		taos->buffer[taos->pos++] = data;
+		if (data == ']') {
+			taos->buffer[taos->pos] = '\0';
+			taos->state = TAOS_STATE_IDLE;
+			wake_up_interruptible(&wq);
+		}
+		break;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/* Extract the adapter name from the buffer received after reset.
+   The buffer is modified and a pointer inside the buffer is returned. */
+static char *taos_adapter_name(char *buffer)
+{
+	char *start, *end;
+
+	start = strstr(buffer, "TAOS ");
+	if (!start)
+		return NULL;
+
+	end = strchr(start, '\r');
+	if (!end)
+		return NULL;
+	*end = '\0';
+
+	return start;
+}
+
+static int taos_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct taos_data *taos;
+	struct i2c_adapter *adapter;
+	char *name;
+	int err;
+
+	taos = kzalloc(sizeof(struct taos_data), GFP_KERNEL);
+	if (!taos) {
+		err = -ENOMEM;
+		goto exit;
+	}
+	taos->state = TAOS_STATE_INIT;
+	serio_set_drvdata(serio, taos);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto exit_kfree;
+
+	adapter = &taos->adapter;
+	adapter->owner = THIS_MODULE;
+	adapter->algo = &taos_algorithm;
+	adapter->algo_data = serio;
+	adapter->dev.parent = &serio->dev;
+
+	/* Reset the TAOS evaluation module to identify it */
+	serio_write(serio, TAOS_CMD_RESET);
+	wait_event_interruptible_timeout(wq, taos->state == TAOS_STATE_IDLE,
+					 msecs_to_jiffies(2000));
+
+	if (taos->state != TAOS_STATE_IDLE) {
+		err = -ENODEV;
+		dev_dbg(&serio->dev, "TAOS EVM reset failed (state=%d, "
+			"pos=%d)\n", taos->state, taos->pos);
+		goto exit_close;
+	}
+
+	name = taos_adapter_name(taos->buffer);
+	if (!name) {
+		err = -ENODEV;
+		dev_err(&serio->dev, "TAOS EVM identification failed\n");
+		goto exit_close;
+	}
+	strlcpy(adapter->name, name, sizeof(adapter->name));
+
+	err = i2c_add_adapter(adapter);
+	if (err)
+		goto exit_close;
+	dev_dbg(&serio->dev, "Connected to TAOS EVM\n");
+
+	taos->client = taos_instantiate_device(adapter);
+	return 0;
+
+ exit_close:
+	serio_close(serio);
+ exit_kfree:
+	serio_set_drvdata(serio, NULL);
+	kfree(taos);
+ exit:
+	return err;
+}
+
+static void taos_disconnect(struct serio *serio)
+{
+	struct taos_data *taos = serio_get_drvdata(serio);
+
+	if (taos->client)
+		i2c_unregister_device(taos->client);
+	i2c_del_adapter(&taos->adapter);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	kfree(taos);
+
+	dev_dbg(&serio->dev, "Disconnected from TAOS EVM\n");
+}
+
+static struct serio_device_id taos_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_TAOSEVM,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+MODULE_DEVICE_TABLE(serio, taos_serio_ids);
+
+static struct serio_driver taos_drv = {
+	.driver		= {
+		.name	= "taos-evm",
+	},
+	.description	= "TAOS evaluation module driver",
+	.id_table	= taos_serio_ids,
+	.connect	= taos_connect,
+	.disconnect	= taos_disconnect,
+	.interrupt	= taos_interrupt,
+};
+
+static int __init taos_init(void)
+{
+	return serio_register_driver(&taos_drv);
+}
+
+static void __exit taos_exit(void)
+{
+	serio_unregister_driver(&taos_drv);
+}
+
+MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
+MODULE_DESCRIPTION("TAOS evaluation module driver");
+MODULE_LICENSE("GPL");
+
+module_init(taos_init);
+module_exit(taos_exit);

include/linux/serio.h

@@ -209,5 +209,6 @@ static inline void serio_unpin_driver(struct serio *serio)
 #define SERIO_PENMOUNT	0x31
 #define SERIO_TOUCHRIGHT	0x32
 #define SERIO_TOUCHWIN	0x33
+#define SERIO_TAOSEVM	0x34
 
 #endif