Re: [PATCH] char/tpm: Add new driver for Infineon I2C TIS TPM

[Andi Shyti]

Hi Peter,

> +/*
> + * Copyright (C) 2012 Infineon Technologies
> + *
> + * Authors:
> + * Peter Huewe <peter.huewe@xxxxxxxxxxxx>
> + *
> + * Device driver for TCG/TCPA TPM (trusted platform module).
> + * Specifications at www.trustedcomputinggroup.org
> + *
> + * This device driver implements the TPM interface as defined in
> + * the TCG TPM Interface Spec version 1.2, revision 1.0 and the
> + * Infineon I2C Protocol Stack Specification v0.20.
> + *
> + * It is based on the original tpm_tis device driver from Leendert van
> + * Dorn and Kyleen Hall.
> + *
> + * 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.
> + *
> + *
> + */
> +#include <linux/init.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/wait.h>
> +#include "tpm.h"
> +
> +/* max. buffer size supported by our tpm */
> +#define TPM_BUFSIZE 1260
> +
> +/* max. number of iterations after i2c NAK */
> +#define MAX_COUNT 3
> +
> +#define SLEEP_DURATION_LOW 55
> +#define SLEEP_DURATION_HI 65
> +
> +/* max. number of iterations after i2c NAK for 'long' commands
> + * we need this especially for sending TPM_READY, since the cleanup after the
> + * transtion to the ready state may take some time, but it is unpredictable
> + * how long it will take.
> + */
> +#define MAX_COUNT_LONG 50
> +
> +#define SLEEP_DURATION_LONG_LOW 200
> +#define SLEEP_DURATION_LONG_HI 220
> +
> +/* expected value for DIDVID register */
> +#define TPM_TIS_I2C_DID_VID 0x000b15d1L
> +
> +/* Structure to store I2C TPM specific stuff */
> +struct tpm_inf_dev {
> +	struct i2c_client *client;
> +	u8 buf[TPM_BUFSIZE+sizeof(u8)]; /* max. buffer size + addr */
> +	struct tpm_chip *chip;
> +};
> +
> +static struct tpm_inf_dev tpm_dev;
> +
> +
> +/*
> + * iic_tpm_read() - read from TPM register
> + * @addr: register address to read from
> + * @buffer: provided by caller
> + * @len: number of bytes to read
> + *
> + * Read len bytes from TPM register and put them into
> + * buffer (little-endian format, i.e. first byte is put into buffer[0]).
> + *
> + * NOTE: TPM is big-endian for multi-byte values. Multi-byte
> + * values have to be swapped.
> + *
> + * Return -EIO on error, 0 on success.
> + */
> +static int iic_tpm_read(u8 addr, u8 *buffer, size_t len)
> +{
> +
> +	struct i2c_msg msg1 = { tpm_dev.client->addr, 0, 1, &addr };
> +	struct i2c_msg msg2 = { tpm_dev.client->addr, I2C_M_RD, len, buffer };
> +
> +	int rc;
> +	int count;
> +
> +	for (count = 0; count < MAX_COUNT; count++) {
> +		rc = i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
> +		if (rc > 0)
> +			break; /* break here to skip sleep */
> +
> +		usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
> +	}

Why don't you use the i2c_smbus* family function to read/write
from i2c. Everything you wrote here is already implemented there,
this is just overcode.

> +
> +	if (rc <= 0)
> +		return -EIO;
> +
> +	/* After the TPM has successfully received the register address it needs
> +	 * some time, thus we're sleeping here again, before retrieving the data
> +	 */
> +	for (count = 0; count < MAX_COUNT; count++) {
> +		usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
> +		rc = i2c_transfer(tpm_dev.client->adapter, &msg2, 1);
> +		if (rc > 0)
> +			break;
> +
> +	}

... same here ...

> +
> +	if (rc <= 0)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int iic_tpm_write_generic(u8 addr, u8 *buffer, size_t len,
> +				unsigned int sleep_low,
> +				unsigned int sleep_hi,
> +				u8 max_count)
> +{
> +	int rc = -1;

Haven't understood why here you are initializing -1

> +	int count;
> +
> +	struct i2c_msg msg1 = { tpm_dev.client->addr, 0, len + 1, tpm_dev.buf };
> +
> +	tpm_dev.buf[0] = addr;
> +	memcpy(&(tpm_dev.buf[1]), buffer, len);
> +
> +	for (count = 0; count < max_count; count++) {
> +		rc = i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
> +		if (rc > 0)
> +			break;
> +
> +		usleep_range(sleep_low, sleep_hi);
> +	}

... same here ...

> +
> +	if (rc <= 0)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +/*
> + * iic_tpm_write() - write to TPM register
> + * @addr: register address to write to
> + * @buffer: containing data to be written
> + * @len: number of bytes to write
> + *
> + * Write len bytes from provided buffer to TPM register (little
> + * endian format, i.e. buffer[0] is written as first byte).
> + *
> + * NOTE: TPM is big-endian for multi-byte values. Multi-byte
> + * values have to be swapped.
> + *
> + * NOTE: use this function instead of the iic_tpm_write_generic function.
> + *
> + * Return -EIO on error, 0 on success
> + */
> +static int iic_tpm_write(u8 addr, u8 *buffer, size_t len)
> +{
> +	return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION_LOW,
> +			SLEEP_DURATION_HI, MAX_COUNT);
> +}
> +
> +/*
> + * This function is needed especially for the cleanup situation after
> + * sending TPM_READY
> + * */
> +static int iic_tpm_write_long(u8 addr, u8 *buffer, size_t len)
> +{
> +	return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION_LONG_LOW,
> +			SLEEP_DURATION_LONG_HI, MAX_COUNT_LONG);
> +}
> +
> +enum tis_access {
> +	TPM_ACCESS_VALID = 0x80,
> +	TPM_ACCESS_ACTIVE_LOCALITY = 0x20,
> +	TPM_ACCESS_REQUEST_PENDING = 0x04,
> +	TPM_ACCESS_REQUEST_USE = 0x02,
> +};
> +
> +enum tis_status {
> +	TPM_STS_VALID = 0x80,
> +	TPM_STS_COMMAND_READY = 0x40,
> +	TPM_STS_GO = 0x20,
> +	TPM_STS_DATA_AVAIL = 0x10,
> +	TPM_STS_DATA_EXPECT = 0x08,
> +};
> +
> +enum tis_defaults {
> +	TIS_SHORT_TIMEOUT = 750,	/* ms */
> +	TIS_LONG_TIMEOUT = 2000,	/* 2 sec */
> +};
> +
> +#define	TPM_ACCESS(l)			(0x0000 | ((l) << 4))
> +#define	TPM_STS(l)			(0x0001 | ((l) << 4))
> +#define	TPM_DATA_FIFO(l)		(0x0005 | ((l) << 4))
> +#define	TPM_DID_VID(l)			(0x0006 | ((l) << 4))
> +
> +static int check_locality(struct tpm_chip *chip, int loc)
> +{
> +	u8 buf;
> +	int rc;
> +
> +	rc = iic_tpm_read(TPM_ACCESS(loc), &buf, 1);
> +	if (rc < 0)
> +		return rc;
> +
> +	if ((buf & (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) ==
> +		(TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) {
> +		chip->vendor.locality = loc;
> +		return loc;
> +	}
> +
> +	return -1;

Please choose a valid errno

> +}
> +
> +static void release_locality(struct tpm_chip *chip, int loc, int force)
> +{
> +	u8 buf;
> +	if (iic_tpm_read(TPM_ACCESS(loc), &buf, 1) < 0)
> +		return;
> +
> +	if (force || (buf & (TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) ==
> +			(TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) {
> +		buf = TPM_ACCESS_ACTIVE_LOCALITY;
> +		iic_tpm_write(TPM_ACCESS(loc), &buf, 1);

here you are ignoring the failure case

> +	}
> +}
> +
> +static int request_locality(struct tpm_chip *chip, int loc)
> +{
> +	unsigned long stop;
> +	u8 buf = TPM_ACCESS_REQUEST_USE;
> +
> +	if (check_locality(chip, loc) >= 0)
> +		return loc;
> +
> +	iic_tpm_write(TPM_ACCESS(loc), &buf, 1);

also here the failure is ignored

> +
> +	/* wait for burstcount */
> +	stop = jiffies + chip->vendor.timeout_a;
> +	do {
> +		if (check_locality(chip, loc) >= 0)
> +			return loc;
> +		msleep(TPM_TIMEOUT);
> +	} while (time_before(jiffies, stop));
> +
> +	return -1;

Please choose a valid errno

> +}
> +
> +static u8 tpm_tis_i2c_status(struct tpm_chip *chip)
> +{
> +	/* NOTE: since i2c read may fail, return 0 in this case --> time-out */
> +	u8 buf;
> +	if (iic_tpm_read(TPM_STS(chip->vendor.locality), &buf, 1) < 0)

I think (but not sure) that this may upset
./scripts/checkpatch.pl

> +		return 0;
> +	else
> +		return buf;
> +}
> +
> +static void tpm_tis_i2c_ready(struct tpm_chip *chip)
> +{
> +	/* this causes the current command to be aborted */
> +	u8 buf = TPM_STS_COMMAND_READY;
> +	iic_tpm_write_long(TPM_STS(chip->vendor.locality), &buf, 1);

Still :) is there any reason you are ignoring the return value
from iic_tpm_write_long?

> +}
> +
> +static ssize_t get_burstcount(struct tpm_chip *chip)
> +{
> +	unsigned long stop;
> +	ssize_t burstcnt;
> +	u8 buf[3];
> +
> +	/* wait for burstcount */
> +	/* which timeout value, spec has 2 answers (c & d) */
> +	stop = jiffies + chip->vendor.timeout_d;
> +	do {
> +		/* Note: STS is little endian */
> +		if (iic_tpm_read(TPM_STS(chip->vendor.locality) + 1, buf, 3) < 0)
> +			burstcnt = 0;
> +		else
> +			burstcnt = (buf[2] << 16) + (buf[1] << 8) + buf[0];
> +
> +		if (burstcnt)
> +			return burstcnt;
> +
> +		msleep(TPM_TIMEOUT);
> +	} while (time_before(jiffies, stop));
> +	return -EBUSY;
> +}
> +
> +static int wait_for_stat(struct tpm_chip *chip, u8 mask, unsigned long timeout,
> +			int *status)
> +{
> +	unsigned long stop;
> +
> +	/* check current status */
> +	*status = tpm_tis_i2c_status(chip);
> +	if ((*status & mask) == mask)
> +		return 0;
> +
> +	stop = jiffies + timeout;
> +	do {
> +		msleep(TPM_TIMEOUT);
> +		*status = tpm_tis_i2c_status(chip);

maybe you should sleep after the i2c_status()

> +		if ((*status & mask) == mask)
> +			return 0;
> +
> +	} while (time_before(jiffies, stop));
> +
> +	return -ETIME;
> +}
> +
> +static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
> +{
> +	size_t size = 0;
> +	ssize_t burstcnt;
> +	int rc;
> +
> +	while (size < count) {
> +		burstcnt = get_burstcount(chip);
> +
> +		/* burstcnt < 0 = tpm is busy */
> +		if (burstcnt < 0)
> +			return burstcnt;
> +
> +		/* limit received data to max. left */
> +		if (burstcnt > (count-size))
> +			burstcnt = count-size;
> +
> +		rc = iic_tpm_read(TPM_DATA_FIFO(chip->vendor.locality),
> +				  &(buf[size]),
> +				  burstcnt);
> +		if (rc == 0)
> +			size += burstcnt;
> +
> +	}
> +	return size;
> +}
> +
> +static int tpm_tis_i2c_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> +{
> +	int size = 0;
> +	int expected, status;
> +
> +	if (count < TPM_HEADER_SIZE) {
> +		size = -EIO;
> +		goto out;
> +	}
> +
> +	/* read first 10 bytes, including tag, paramsize, and result */
> +	size = recv_data(chip, buf, TPM_HEADER_SIZE);
> +	if (size < TPM_HEADER_SIZE) {
> +		dev_err(chip->dev, "Unable to read header\n");
> +		goto out;
> +	}
> +
> +	expected = be32_to_cpu(*(__be32 *) (buf + 2));
> +	if ((size_t)expected > count) {
> +		size = -EIO;
> +		goto out;
> +	}
> +
> +	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
> +				expected - TPM_HEADER_SIZE);
> +	if (size < expected) {
> +		dev_err(chip->dev, "Unable to read remainder of result\n");
> +		size = -ETIME;
> +		goto out;
> +	}
> +
> +	wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c, &status);
> +	if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
> +		dev_err(chip->dev, "Error left over data\n");
> +		size = -EIO;
> +		goto out;
> +	}
> +
> +out:
> +	tpm_tis_i2c_ready(chip);
> +	/* The TPM needs some time to clean up here,
> +	 * so we sleep rather than keeping the bus busy
> +	 */
> +	usleep_range(2400, 2600);
> +	release_locality(chip, chip->vendor.locality, 0);
> +	return size;
> +}
> +
> +static int tpm_tis_i2c_send(struct tpm_chip *chip, u8 *buf, size_t len)
> +{
> +	int rc, status;
> +	ssize_t burstcnt;
> +	size_t count = 0;
> +	u8 sts = TPM_STS_GO;
> +
> +	if (len > TPM_BUFSIZE)
> +		return -E2BIG; /* command is too long for our tpm, sorry */
> +
> +	if (request_locality(chip, 0) < 0)
> +		return -EBUSY;
> +
> +	status = tpm_tis_i2c_status(chip);
> +	if ((status & TPM_STS_COMMAND_READY) == 0) {
> +		tpm_tis_i2c_ready(chip);
> +		if (wait_for_stat
> +		    (chip, TPM_STS_COMMAND_READY,
> +		     chip->vendor.timeout_b, &status) < 0) {
> +			rc = -ETIME;
> +			goto out_err;
> +		}
> +	}
> +
> +	while (count < len - 1) {
> +		burstcnt = get_burstcount(chip);
> +		dev_dbg(chip->dev,
> +			"send(): count=%zd, len=%zd, burstcount=%zd (plain)\n",
> +			count, len, burstcnt);
> +
> +		/* burstcnt < 0 = tpm is busy */
> +		if (burstcnt < 0)
> +			return burstcnt;
> +
> +		if (burstcnt > (len-1-count))
> +			burstcnt = len-1-count;
> +
> +		dev_dbg(chip->dev, "send(): burstcount=%zd\n", burstcnt);
> +
> +		rc = iic_tpm_write(TPM_DATA_FIFO(chip->vendor.locality),
> +				   &(buf[count]), burstcnt);
> +		if (rc == 0)
> +			count += burstcnt;
> +
> +		wait_for_stat(chip, TPM_STS_VALID,
> +				chip->vendor.timeout_c, &status);
> +
> +		if ((status & TPM_STS_DATA_EXPECT) == 0) {
> +			rc = -EIO;
> +			goto out_err;
> +		}
> +
> +	}
> +
> +	dev_dbg(chip->dev, "send(): last byte @ count=%zd\n", count);
> +
> +	/* write last byte */
> +	iic_tpm_write(TPM_DATA_FIFO(chip->vendor.locality), &(buf[count]), 1);
> +	wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c, &status);
> +	if ((status & TPM_STS_DATA_EXPECT) != 0) {
> +		rc = -EIO;
> +		goto out_err;
> +	}
> +
> +	/* go and do it */
> +	iic_tpm_write(TPM_STS(chip->vendor.locality), &sts, 1);
> +
> +	return len;
> +out_err:
> +	tpm_tis_i2c_ready(chip);
> +	/* The TPM needs some time to clean up here,
> +	 * so we sleep rather than keeping the bus busy
> +	 */
> +	usleep_range(2400, 2600);
> +	release_locality(chip, chip->vendor.locality, 0);
> +	return rc;
> +}
> +
> +static const struct file_operations tis_ops = {
> +	.owner = THIS_MODULE,
> +	.llseek = no_llseek,
> +	.open = tpm_open,
> +	.read = tpm_read,
> +	.write = tpm_write,
> +	.release = tpm_release,
> +};
> +
> +static DEVICE_ATTR(pubek, S_IRUGO, tpm_show_pubek, NULL);
> +static DEVICE_ATTR(pcrs, S_IRUGO, tpm_show_pcrs, NULL);
> +static DEVICE_ATTR(enabled, S_IRUGO, tpm_show_enabled, NULL);
> +static DEVICE_ATTR(active, S_IRUGO, tpm_show_active, NULL);
> +static DEVICE_ATTR(owned, S_IRUGO, tpm_show_owned, NULL);
> +static DEVICE_ATTR(temp_deactivated, S_IRUGO, tpm_show_temp_deactivated, NULL);
> +static DEVICE_ATTR(caps, S_IRUGO, tpm_show_caps_1_2, NULL);
> +static DEVICE_ATTR(cancel, S_IWUSR | S_IWGRP, NULL, tpm_store_cancel);
> +static DEVICE_ATTR(durations, S_IRUGO, tpm_show_durations, NULL);
> +static DEVICE_ATTR(timeouts, S_IRUGO, tpm_show_timeouts, NULL);
> +
> +static struct attribute *tis_attrs[] = {
> +	&dev_attr_pubek.attr,
> +	&dev_attr_pcrs.attr,
> +	&dev_attr_enabled.attr,
> +	&dev_attr_active.attr,
> +	&dev_attr_owned.attr,
> +	&dev_attr_temp_deactivated.attr,
> +	&dev_attr_caps.attr,
> +	&dev_attr_cancel.attr,
> +	&dev_attr_durations.attr,
> +	&dev_attr_timeouts.attr, NULL,
> +};
> +
> +static struct attribute_group tis_attr_grp = {
> +	.attrs = tis_attrs
> +};
> +
> +static struct tpm_vendor_specific tpm_tis_i2c = {
> +	.status = tpm_tis_i2c_status,
> +	.recv = tpm_tis_i2c_recv,
> +	.send = tpm_tis_i2c_send,
> +	.cancel = tpm_tis_i2c_ready,
> +	.req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +	.req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +	.req_canceled = TPM_STS_COMMAND_READY,
> +	.attr_group = &tis_attr_grp,
> +	.miscdev = {
> +		    .fops = &tis_ops,},
> +};
> +
> +static int tpm_tis_i2c_init(struct device *dev)
> +{
> +	u32 vendor;
> +	int rc = 0;
> +	struct tpm_chip *chip;
> +
> +	chip = tpm_register_hardware(dev, &tpm_tis_i2c);
> +	if (!chip) {
> +		rc = -ENODEV;
> +		goto out_err;
> +	}
> +
> +	/* Disable interrupts */
> +	chip->vendor.irq = 0;
> +
> +	/* Default timeouts */
> +	chip->vendor.timeout_a = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
> +	chip->vendor.timeout_b = msecs_to_jiffies(TIS_LONG_TIMEOUT);
> +	chip->vendor.timeout_c = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
> +	chip->vendor.timeout_d = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
> +
> +	if (request_locality(chip, 0) != 0) {
> +		rc = -ENODEV;
> +		goto out_vendor;
> +	}
> +
> +	/* read four bytes from DID_VID register */
> +	if (iic_tpm_read(TPM_DID_VID(0), (u8 *) &vendor, 4) < 0) {
> +		rc = -EIO;
> +		goto out_vendor;
> +	}
> +
> +	/* create DID_VID register value, after swapping to little-endian */
> +	vendor = be32_to_cpu((__be32) vendor);
> +
> +	if (vendor != TPM_TIS_I2C_DID_VID) {
> +		rc = -ENODEV;
> +		goto out_release;
> +	}
> +
> +	dev_info(dev, "1.2 TPM (device-id 0x%X)\n", vendor >> 16);
> +
> +	INIT_LIST_HEAD(&chip->vendor.list);
> +	tpm_dev.chip = chip;
> +
> +	tpm_get_timeouts(chip);
> +	tpm_do_selftest(chip);
> +
> +	return 0;
> +
> +out_release:
> +	release_locality(chip, chip->vendor.locality, 1);
> +
> +out_vendor:
> +	tpm_dev_vendor_release(chip);
> +	tpm_remove_hardware(chip->dev);
> +
> +out_err:
> +	return rc;
> +}
> +
> +  <------

Just to be strict... in case you'll resend the patch, there is
one blank line more than necessary :)

> +static const struct i2c_device_id tpm_i2c_tis_table[] = {
> +	{ "tpm_tis_i2c", 0 },
> +	{ },
> +};
> +
> +#ifdef CONFIG_PM

and what if CONFIG_PM is not defined?

> +/* NOTE:
> + * Suspend does currently not work Nvidias Tegra2 Platform
> + * but works fine on Beagleboard (arm omap).
> + *
> + * This function will block System Suspend if TPM is not initialized,
> + * however the TPM is usually initialized by BIOS/u-boot or by sending
> + * a tpm startup command.
> + */
> +static int tpm_tis_i2c_suspend(struct device *dev)
> +{
> +	return tpm_pm_suspend(dev, dev->power.power_state);
> +}
> +
> +static int tpm_tis_i2c_resume(struct device *dev)
> +{
> +	return tpm_pm_resume(dev);
> +}
> +
> +static const struct dev_pm_ops tpm_tis_i2c_ops = {
> +	.suspend = tpm_tis_i2c_suspend,
> +	.resume = tpm_tis_i2c_resume,
> +};
> +#endif
> +
> +
> +static int dummy_probe(struct i2c_client *client,
> +	const struct i2c_device_id *id)
> +{
> +	return 0;
> +}
> +
> +static int dummy_remove(struct i2c_client *client)
> +{
> +	return 0;
> +}

Ignoring probe and remove, is a matter of choice, but to me looks
awful.

> +static struct i2c_driver tpm_i2c_tis_driver = {
> +
> +	.id_table = tpm_i2c_tis_table,
> +	.probe = dummy_probe,
> +	.remove = dummy_remove,
> +	.driver	= {
> +		.name	= "tpm_tis_i2c",
> +		.owner	= THIS_MODULE,
> +#ifdef CONFIG_PM
> +		.pm     = &tpm_tis_i2c_ops,
> +#endif
> +	},
> +};
> +
> +
> +static struct i2c_adapter *adap;
> +static struct i2c_client *client;
> +static	struct i2c_board_info info = {
> +	I2C_BOARD_INFO("tpm_tis_i2c", 0x20),
> +};
> +
> +
> +static int addr = 0x20;
> +module_param(addr, int, S_IRUGO);
> +MODULE_PARM_DESC(addr, "TPM I2C Device Address (default: 0x20)");
> +
> +static int bus_id = 2;
> +module_param(bus_id, int, S_IRUGO);
> +MODULE_PARM_DESC(bus_id, "TPM I2C Bus Id (default: 2)");
> +
> +static int __init init_tis_i2c(void)
> +{
> +
> +	int rc = 0;
> +	info.addr = addr;
> +
> +
> +	if (tpm_dev.client != NULL)
> +		return -EBUSY;
> +
> +	adap = i2c_get_adapter(bus_id);
> +	if (!adap)
> +		return -ENODEV;
> +
> +	client = i2c_new_device(adap, &info);
> +	if (!client) {
> +		i2c_put_adapter(adap);
> +		return -ENODEV;
> +	}
> +
> +	rc = i2c_add_driver(&tpm_i2c_tis_driver);
> +	if (rc != 0) {
> +		i2c_del_driver(&tpm_i2c_tis_driver);
> +		i2c_put_adapter(tpm_dev.client->adapter);
> +		return -ENODEV;
> +	}
> +	client->driver = &tpm_i2c_tis_driver;
> +
> +	tpm_dev.client = client;
> +
> +	rc = tpm_tis_i2c_init(&client->dev);
> +	if (rc < 0) {
> +		i2c_del_driver(&tpm_i2c_tis_driver);
> +		i2c_put_adapter(tpm_dev.client->adapter);
> +		device_del(&(tpm_dev.client->dev));
> +	}
> +
> +	return rc;
> +}

I think this should be done in the probe function. Moreover you
are also not checking the functionalities of the i2c drivers.

> +
> +static void __exit cleanup_tis_i2c(void)
> +{
> +	struct tpm_chip *chip = tpm_dev.chip;
> +	release_locality(chip, chip->vendor.locality, 1);
> +
> +	tpm_dev_vendor_release(chip);
> +	tpm_remove_hardware(chip->dev);
> +
> +	i2c_del_driver(&tpm_i2c_tis_driver);
> +
> +	i2c_put_adapter(tpm_dev.client->adapter);
> +
> +	/*
> +	 * taken from core.c as workaround since
> +	 * tpm_remove_hardware requires device structure
> +	 */
> +	pr_debug("device: '%s': %s\n",
> +		dev_name(&(tpm_dev.client->dev)), __func__);
> +	device_del(&(tpm_dev.client->dev));
> +}

Still this should be done in the remove function

> +
> +module_init(init_tis_i2c);
> +module_exit(cleanup_tis_i2c);

The correct way of doing this is by using module_i2c_driver()

> +MODULE_AUTHOR("Peter Huewe <peter.huewe@xxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("TPM TIS I2C Driver");
> +MODULE_VERSION("2.1.3");
> +MODULE_LICENSE("GPL");
> -- 
> 1.7.6.msysgit.0
> 
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