drivers/i2c/busses/i2c-isch.c - linux - Git at Google

 /*
     i2c-isch.c - Linux kernel driver for Intel SCH chipset SMBus
     - Based on i2c-piix4.c
     Copyright (c) 1998 - 2002 Frodo Looijaard <frodol@dds.nl> and
     Philip Edelbrock <phil@netroedge.com>
     - Intel SCH support
     Copyright (c) 2007 - 2008 Jacob Jun Pan <jacob.jun.pan@intel.com>

     This program is free software; you can redistribute it and/or modify
     it under the terms 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.
 */

 /*
    Supports:
 	Intel SCH chipsets (AF82US15W, AF82US15L, AF82UL11L)
    Note: we assume there can only be one device, with one SMBus interface.
 */

 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/stddef.h>
 #include <linux/ioport.h>
 #include <linux/i2c.h>
 #include <linux/io.h>
 #include <linux/acpi.h>

 /* SCH SMBus address offsets */
 #define SMBHSTCNT	(0 + sch_smba)
 #define SMBHSTSTS	(1 + sch_smba)
 #define SMBHSTCLK	(2 + sch_smba)
 #define SMBHSTADD	(4 + sch_smba) /* TSA */
 #define SMBHSTCMD	(5 + sch_smba)
 #define SMBHSTDAT0	(6 + sch_smba)
 #define SMBHSTDAT1	(7 + sch_smba)
 #define SMBBLKDAT	(0x20 + sch_smba)

 /* Other settings */
 #define MAX_RETRIES	5000

 /* I2C constants */
 #define SCH_QUICK		0x00
 #define SCH_BYTE		0x01
 #define SCH_BYTE_DATA		0x02
 #define SCH_WORD_DATA		0x03
 #define SCH_BLOCK_DATA		0x05

 static unsigned short sch_smba;
 static struct i2c_adapter sch_adapter;
 static int backbone_speed = 33000; /* backbone speed in kHz */
 module_param(backbone_speed, int, S_IRUSR | S_IWUSR);
 MODULE_PARM_DESC(backbone_speed, "Backbone speed in kHz, (default = 33000)");

 /*
  * Start the i2c transaction -- the i2c_access will prepare the transaction
  * and this function will execute it.
  * return 0 for success and others for failure.
  */
 static int sch_transaction(void)
 {
 	int temp;
 	int result = 0;
 	int retries = 0;

 	dev_dbg(&sch_adapter.dev, "Transaction (pre): CNT=%02x, CMD=%02x, "
 		"ADD=%02x, DAT0=%02x, DAT1=%02x\n", inb(SMBHSTCNT),
 		inb(SMBHSTCMD), inb(SMBHSTADD), inb(SMBHSTDAT0),
 		inb(SMBHSTDAT1));

 	/* Make sure the SMBus host is ready to start transmitting */
 	temp = inb(SMBHSTSTS) & 0x0f;
 	if (temp) {
 		/* Can not be busy since we checked it in sch_access */
 		if (temp & 0x01) {
 			dev_dbg(&sch_adapter.dev, "Completion (%02x). "
 				"Clear...\n", temp);
 		}
 		if (temp & 0x06) {
 			dev_dbg(&sch_adapter.dev, "SMBus error (%02x). "
 				"Resetting...\n", temp);
 		}
 		outb(temp, SMBHSTSTS);
 		temp = inb(SMBHSTSTS) & 0x0f;
 		if (temp) {
 			dev_err(&sch_adapter.dev,
 				"SMBus is not ready: (%02x)\n", temp);
 			return -EAGAIN;
 		}
 	}

 	/* start the transaction by setting bit 4 */
 	outb(inb(SMBHSTCNT) | 0x10, SMBHSTCNT);

 	do {
 		usleep_range(100, 200);
 		temp = inb(SMBHSTSTS) & 0x0f;
 	} while ((temp & 0x08) && (retries++ < MAX_RETRIES));

 	/* If the SMBus is still busy, we give up */
 	if (retries > MAX_RETRIES) {
 		dev_err(&sch_adapter.dev, "SMBus Timeout!\n");
 		result = -ETIMEDOUT;
 	}
 	if (temp & 0x04) {
 		result = -EIO;
 		dev_dbg(&sch_adapter.dev, "Bus collision! SMBus may be "
 			"locked until next hard reset. (sorry!)\n");
 		/* Clock stops and slave is stuck in mid-transmission */
 	} else if (temp & 0x02) {
 		result = -EIO;
 		dev_err(&sch_adapter.dev, "Error: no response!\n");
 	} else if (temp & 0x01) {
 		dev_dbg(&sch_adapter.dev, "Post complete!\n");
 		outb(temp, SMBHSTSTS);
 		temp = inb(SMBHSTSTS) & 0x07;
 		if (temp & 0x06) {
 			/* Completion clear failed */
 			dev_dbg(&sch_adapter.dev, "Failed reset at end of "
 				"transaction (%02x), Bus error!\n", temp);
 		}
 	} else {
 		result = -ENXIO;
 		dev_dbg(&sch_adapter.dev, "No such address.\n");
 	}
 	dev_dbg(&sch_adapter.dev, "Transaction (post): CNT=%02x, CMD=%02x, "
 		"ADD=%02x, DAT0=%02x, DAT1=%02x\n", inb(SMBHSTCNT),
 		inb(SMBHSTCMD), inb(SMBHSTADD), inb(SMBHSTDAT0),
 		inb(SMBHSTDAT1));
 	return result;
 }

 /*
  * This is the main access entry for i2c-sch access
  * adap is i2c_adapter pointer, addr is the i2c device bus address, read_write
  * (0 for read and 1 for write), size is i2c transaction type and data is the
  * union of transaction for data to be transferred or data read from bus.
  * return 0 for success and others for failure.
  */
 static s32 sch_access(struct i2c_adapter *adap, u16 addr,
 		 unsigned short flags, char read_write,
 		 u8 command, int size, union i2c_smbus_data *data)
 {
 	int i, len, temp, rc;

 	/* Make sure the SMBus host is not busy */
 	temp = inb(SMBHSTSTS) & 0x0f;
 	if (temp & 0x08) {
 		dev_dbg(&sch_adapter.dev, "SMBus busy (%02x)\n", temp);
 		return -EAGAIN;
 	}
 	temp = inw(SMBHSTCLK);
 	if (!temp) {
 		/*
 		 * We can't determine if we have 33 or 25 MHz clock for
 		 * SMBus, so expect 33 MHz and calculate a bus clock of
 		 * 100 kHz. If we actually run at 25 MHz the bus will be
 		 * run ~75 kHz instead which should do no harm.
 		 */
 		dev_notice(&sch_adapter.dev,
 			"Clock divider unitialized. Setting defaults\n");
 		outw(backbone_speed / (4 * 100), SMBHSTCLK);
 	}

 	dev_dbg(&sch_adapter.dev, "access size: %d %s\n", size,
 		(read_write)?"READ":"WRITE");
 	switch (size) {
 	case I2C_SMBUS_QUICK:
 		outb((addr << 1) | read_write, SMBHSTADD);
 		size = SCH_QUICK;
 		break;
 	case I2C_SMBUS_BYTE:
 		outb((addr << 1) | read_write, SMBHSTADD);
 		if (read_write == I2C_SMBUS_WRITE)
 			outb(command, SMBHSTCMD);
 		size = SCH_BYTE;
 		break;
 	case I2C_SMBUS_BYTE_DATA:
 		outb((addr << 1) | read_write, SMBHSTADD);
 		outb(command, SMBHSTCMD);
 		if (read_write == I2C_SMBUS_WRITE)
 			outb(data->byte, SMBHSTDAT0);
 		size = SCH_BYTE_DATA;
 		break;
 	case I2C_SMBUS_WORD_DATA:
 		outb((addr << 1) | read_write, SMBHSTADD);
 		outb(command, SMBHSTCMD);
 		if (read_write == I2C_SMBUS_WRITE) {
 			outb(data->word & 0xff, SMBHSTDAT0);
 			outb((data->word & 0xff00) >> 8, SMBHSTDAT1);
 		}
 		size = SCH_WORD_DATA;
 		break;
 	case I2C_SMBUS_BLOCK_DATA:
 		outb((addr << 1) | read_write, SMBHSTADD);
 		outb(command, SMBHSTCMD);
 		if (read_write == I2C_SMBUS_WRITE) {
 			len = data->block[0];
 			if (len == 0 || len > I2C_SMBUS_BLOCK_MAX)
 				return -EINVAL;
 			outb(len, SMBHSTDAT0);
 			for (i = 1; i <= len; i++)
 				outb(data->block[i], SMBBLKDAT+i-1);
 		}
 		size = SCH_BLOCK_DATA;
 		break;
 	default:
 		dev_warn(&adap->dev, "Unsupported transaction %d\n", size);
 		return -EOPNOTSUPP;
 	}
 	dev_dbg(&sch_adapter.dev, "write size %d to 0x%04x\n", size, SMBHSTCNT);
 	outb((inb(SMBHSTCNT) & 0xb0) | (size & 0x7), SMBHSTCNT);

 	rc = sch_transaction();
 	if (rc)	/* Error in transaction */
 		return rc;

 	if ((read_write == I2C_SMBUS_WRITE) || (size == SCH_QUICK))
 		return 0;

 	switch (size) {
 	case SCH_BYTE:
 	case SCH_BYTE_DATA:
 		data->byte = inb(SMBHSTDAT0);
 		break;
 	case SCH_WORD_DATA:
 		data->word = inb(SMBHSTDAT0) + (inb(SMBHSTDAT1) << 8);
 		break;
 	case SCH_BLOCK_DATA:
 		data->block[0] = inb(SMBHSTDAT0);
 		if (data->block[0] == 0 || data->block[0] > I2C_SMBUS_BLOCK_MAX)
 			return -EPROTO;
 		for (i = 1; i <= data->block[0]; i++)
 			data->block[i] = inb(SMBBLKDAT+i-1);
 		break;
 	}
 	return 0;
 }

 static u32 sch_func(struct i2c_adapter *adapter)
 {
 	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
 	    I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
 	    I2C_FUNC_SMBUS_BLOCK_DATA;
 }

 static const struct i2c_algorithm smbus_algorithm = {
 	.smbus_xfer	= sch_access,
 	.functionality	= sch_func,
 };

 static struct i2c_adapter sch_adapter = {
 	.owner		= THIS_MODULE,
 	.class		= I2C_CLASS_HWMON | I2C_CLASS_SPD,
 	.algo		= &smbus_algorithm,
 };

 static int smbus_sch_probe(struct platform_device *dev)
 {
 	struct resource *res;
 	int retval;

 	res = platform_get_resource(dev, IORESOURCE_IO, 0);
 	if (!res)
 		return -EBUSY;

 	if (!devm_request_region(&dev->dev, res->start, resource_size(res),
 				 dev->name)) {
 		dev_err(&dev->dev, "SMBus region 0x%x already in use!\n",
 			sch_smba);
 		return -EBUSY;
 	}

 	sch_smba = res->start;

 	dev_dbg(&dev->dev, "SMBA = 0x%X\n", sch_smba);

 	/* set up the sysfs linkage to our parent device */
 	sch_adapter.dev.parent = &dev->dev;

 	snprintf(sch_adapter.name, sizeof(sch_adapter.name),
 		"SMBus SCH adapter at %04x", sch_smba);

 	retval = i2c_add_adapter(&sch_adapter);
 	if (retval)
 		sch_smba = 0;

 	return retval;
 }

 static int smbus_sch_remove(struct platform_device *pdev)
 {
 	if (sch_smba) {
 		i2c_del_adapter(&sch_adapter);
 		sch_smba = 0;
 	}

 	return 0;
 }

 static struct platform_driver smbus_sch_driver = {
 	.driver = {
 		.name = "isch_smbus",
 	},
 	.probe		= smbus_sch_probe,
 	.remove		= smbus_sch_remove,
 };

 module_platform_driver(smbus_sch_driver);

 MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@intel.com>");
 MODULE_DESCRIPTION("Intel SCH SMBus driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:isch_smbus");
	/*
	i2c-isch.c - Linux kernel driver for Intel SCH chipset SMBus
	- Based on i2c-piix4.c
	Copyright (c) 1998 - 2002 Frodo Looijaard <frodol@dds.nl> and
	Philip Edelbrock <phil@netroedge.com>
	- Intel SCH support
	Copyright (c) 2007 - 2008 Jacob Jun Pan <jacob.jun.pan@intel.com>

	This program is free software; you can redistribute it and/or modify
	it under the terms 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.
	*/

	/*
	Supports:
	Intel SCH chipsets (AF82US15W, AF82US15L, AF82UL11L)
	Note: we assume there can only be one device, with one SMBus interface.
	*/

	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/kernel.h>
	#include <linux/delay.h>
	#include <linux/stddef.h>
	#include <linux/ioport.h>
	#include <linux/i2c.h>
	#include <linux/io.h>
	#include <linux/acpi.h>

	/* SCH SMBus address offsets */
	#define SMBHSTCNT (0 + sch_smba)
	#define SMBHSTSTS (1 + sch_smba)
	#define SMBHSTCLK (2 + sch_smba)
	#define SMBHSTADD (4 + sch_smba) /* TSA */
	#define SMBHSTCMD (5 + sch_smba)
	#define SMBHSTDAT0 (6 + sch_smba)
	#define SMBHSTDAT1 (7 + sch_smba)
	#define SMBBLKDAT (0x20 + sch_smba)

	/* Other settings */
	#define MAX_RETRIES 5000

	/* I2C constants */
	#define SCH_QUICK 0x00
	#define SCH_BYTE 0x01
	#define SCH_BYTE_DATA 0x02
	#define SCH_WORD_DATA 0x03
	#define SCH_BLOCK_DATA 0x05

	static unsigned short sch_smba;
	static struct i2c_adapter sch_adapter;
	static int backbone_speed = 33000; /* backbone speed in kHz */
	module_param(backbone_speed, int, S_IRUSR \| S_IWUSR);
	MODULE_PARM_DESC(backbone_speed, "Backbone speed in kHz, (default = 33000)");

	/*
	* Start the i2c transaction -- the i2c_access will prepare the transaction
	* and this function will execute it.
	* return 0 for success and others for failure.
	*/
	static int sch_transaction(void)
	{
	int temp;
	int result = 0;
	int retries = 0;

	dev_dbg(&sch_adapter.dev, "Transaction (pre): CNT=%02x, CMD=%02x, "
	"ADD=%02x, DAT0=%02x, DAT1=%02x\n", inb(SMBHSTCNT),
	inb(SMBHSTCMD), inb(SMBHSTADD), inb(SMBHSTDAT0),
	inb(SMBHSTDAT1));

	/* Make sure the SMBus host is ready to start transmitting */
	temp = inb(SMBHSTSTS) & 0x0f;
	if (temp) {
	/* Can not be busy since we checked it in sch_access */
	if (temp & 0x01) {
	dev_dbg(&sch_adapter.dev, "Completion (%02x). "
	"Clear...\n", temp);
	}
	if (temp & 0x06) {
	dev_dbg(&sch_adapter.dev, "SMBus error (%02x). "
	"Resetting...\n", temp);
	}
	outb(temp, SMBHSTSTS);
	temp = inb(SMBHSTSTS) & 0x0f;
	if (temp) {
	dev_err(&sch_adapter.dev,
	"SMBus is not ready: (%02x)\n", temp);
	return -EAGAIN;
	}
	}

	/* start the transaction by setting bit 4 */
	outb(inb(SMBHSTCNT) \| 0x10, SMBHSTCNT);

	do {
	usleep_range(100, 200);
	temp = inb(SMBHSTSTS) & 0x0f;
	} while ((temp & 0x08) && (retries++ < MAX_RETRIES));

	/* If the SMBus is still busy, we give up */
	if (retries > MAX_RETRIES) {
	dev_err(&sch_adapter.dev, "SMBus Timeout!\n");
	result = -ETIMEDOUT;
	}
	if (temp & 0x04) {
	result = -EIO;
	dev_dbg(&sch_adapter.dev, "Bus collision! SMBus may be "
	"locked until next hard reset. (sorry!)\n");
	/* Clock stops and slave is stuck in mid-transmission */
	} else if (temp & 0x02) {
	result = -EIO;
	dev_err(&sch_adapter.dev, "Error: no response!\n");
	} else if (temp & 0x01) {
	dev_dbg(&sch_adapter.dev, "Post complete!\n");
	outb(temp, SMBHSTSTS);
	temp = inb(SMBHSTSTS) & 0x07;
	if (temp & 0x06) {
	/* Completion clear failed */
	dev_dbg(&sch_adapter.dev, "Failed reset at end of "
	"transaction (%02x), Bus error!\n", temp);
	}
	} else {
	result = -ENXIO;
	dev_dbg(&sch_adapter.dev, "No such address.\n");
	}
	dev_dbg(&sch_adapter.dev, "Transaction (post): CNT=%02x, CMD=%02x, "
	"ADD=%02x, DAT0=%02x, DAT1=%02x\n", inb(SMBHSTCNT),
	inb(SMBHSTCMD), inb(SMBHSTADD), inb(SMBHSTDAT0),
	inb(SMBHSTDAT1));
	return result;
	}

	/*
	* This is the main access entry for i2c-sch access
	* adap is i2c_adapter pointer, addr is the i2c device bus address, read_write
	* (0 for read and 1 for write), size is i2c transaction type and data is the
	* union of transaction for data to be transferred or data read from bus.
	* return 0 for success and others for failure.
	*/
	static s32 sch_access(struct i2c_adapter *adap, u16 addr,
	unsigned short flags, char read_write,
	u8 command, int size, union i2c_smbus_data *data)
	{
	int i, len, temp, rc;

	/* Make sure the SMBus host is not busy */
	temp = inb(SMBHSTSTS) & 0x0f;
	if (temp & 0x08) {
	dev_dbg(&sch_adapter.dev, "SMBus busy (%02x)\n", temp);
	return -EAGAIN;
	}
	temp = inw(SMBHSTCLK);
	if (!temp) {
	/*
	* We can't determine if we have 33 or 25 MHz clock for
	* SMBus, so expect 33 MHz and calculate a bus clock of
	* 100 kHz. If we actually run at 25 MHz the bus will be
	* run ~75 kHz instead which should do no harm.
	*/
	dev_notice(&sch_adapter.dev,
	"Clock divider unitialized. Setting defaults\n");
	outw(backbone_speed / (4 * 100), SMBHSTCLK);
	}

	dev_dbg(&sch_adapter.dev, "access size: %d %s\n", size,
	(read_write)?"READ":"WRITE");
	switch (size) {
	case I2C_SMBUS_QUICK:
	outb((addr << 1) \| read_write, SMBHSTADD);
	size = SCH_QUICK;
	break;
	case I2C_SMBUS_BYTE:
	outb((addr << 1) \| read_write, SMBHSTADD);
	if (read_write == I2C_SMBUS_WRITE)
	outb(command, SMBHSTCMD);
	size = SCH_BYTE;
	break;
	case I2C_SMBUS_BYTE_DATA:
	outb((addr << 1) \| read_write, SMBHSTADD);
	outb(command, SMBHSTCMD);
	if (read_write == I2C_SMBUS_WRITE)
	outb(data->byte, SMBHSTDAT0);
	size = SCH_BYTE_DATA;
	break;
	case I2C_SMBUS_WORD_DATA:
	outb((addr << 1) \| read_write, SMBHSTADD);
	outb(command, SMBHSTCMD);
	if (read_write == I2C_SMBUS_WRITE) {
	outb(data->word & 0xff, SMBHSTDAT0);
	outb((data->word & 0xff00) >> 8, SMBHSTDAT1);
	}
	size = SCH_WORD_DATA;
	break;
	case I2C_SMBUS_BLOCK_DATA:
	outb((addr << 1) \| read_write, SMBHSTADD);
	outb(command, SMBHSTCMD);
	if (read_write == I2C_SMBUS_WRITE) {
	len = data->block[0];
	if (len == 0 \|\| len > I2C_SMBUS_BLOCK_MAX)
	return -EINVAL;
	outb(len, SMBHSTDAT0);
	for (i = 1; i <= len; i++)
	outb(data->block[i], SMBBLKDAT+i-1);
	}
	size = SCH_BLOCK_DATA;
	break;
	default:
	dev_warn(&adap->dev, "Unsupported transaction %d\n", size);
	return -EOPNOTSUPP;
	}
	dev_dbg(&sch_adapter.dev, "write size %d to 0x%04x\n", size, SMBHSTCNT);
	outb((inb(SMBHSTCNT) & 0xb0) \| (size & 0x7), SMBHSTCNT);

	rc = sch_transaction();
	if (rc) /* Error in transaction */
	return rc;

	if ((read_write == I2C_SMBUS_WRITE) \|\| (size == SCH_QUICK))
	return 0;

	switch (size) {
	case SCH_BYTE:
	case SCH_BYTE_DATA:
	data->byte = inb(SMBHSTDAT0);
	break;
	case SCH_WORD_DATA:
	data->word = inb(SMBHSTDAT0) + (inb(SMBHSTDAT1) << 8);
	break;
	case SCH_BLOCK_DATA:
	data->block[0] = inb(SMBHSTDAT0);
	if (data->block[0] == 0 \|\| data->block[0] > I2C_SMBUS_BLOCK_MAX)
	return -EPROTO;
	for (i = 1; i <= data->block[0]; i++)
	data->block[i] = inb(SMBBLKDAT+i-1);
	break;
	}
	return 0;
	}

	static u32 sch_func(struct i2c_adapter *adapter)
	{
	return I2C_FUNC_SMBUS_QUICK \| I2C_FUNC_SMBUS_BYTE \|
	I2C_FUNC_SMBUS_BYTE_DATA \| I2C_FUNC_SMBUS_WORD_DATA \|
	I2C_FUNC_SMBUS_BLOCK_DATA;
	}

	static const struct i2c_algorithm smbus_algorithm = {
	.smbus_xfer = sch_access,
	.functionality = sch_func,
	};

	static struct i2c_adapter sch_adapter = {
	.owner = THIS_MODULE,
	.class = I2C_CLASS_HWMON \| I2C_CLASS_SPD,
	.algo = &smbus_algorithm,
	};

	static int smbus_sch_probe(struct platform_device *dev)
	{
	struct resource *res;
	int retval;

	res = platform_get_resource(dev, IORESOURCE_IO, 0);
	if (!res)
	return -EBUSY;

	if (!devm_request_region(&dev->dev, res->start, resource_size(res),
	dev->name)) {
	dev_err(&dev->dev, "SMBus region 0x%x already in use!\n",
	sch_smba);
	return -EBUSY;
	}

	sch_smba = res->start;

	dev_dbg(&dev->dev, "SMBA = 0x%X\n", sch_smba);

	/* set up the sysfs linkage to our parent device */
	sch_adapter.dev.parent = &dev->dev;

	snprintf(sch_adapter.name, sizeof(sch_adapter.name),
	"SMBus SCH adapter at %04x", sch_smba);

	retval = i2c_add_adapter(&sch_adapter);
	if (retval)
	sch_smba = 0;

	return retval;
	}

	static int smbus_sch_remove(struct platform_device *pdev)
	{
	if (sch_smba) {
	i2c_del_adapter(&sch_adapter);
	sch_smba = 0;
	}

	return 0;
	}

	static struct platform_driver smbus_sch_driver = {
	.driver = {
	.name = "isch_smbus",
	},
	.probe = smbus_sch_probe,
	.remove = smbus_sch_remove,
	};

	module_platform_driver(smbus_sch_driver);

	MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@intel.com>");
	MODULE_DESCRIPTION("Intel SCH SMBus driver");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:isch_smbus");