Date:	Mon, 22 Sep 2014 13:30:26 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Muthu Mani <muth@...ress.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-gpio@...r.kernel.org, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rajaram Regupathy <rera@...ress.com>
Subject: Re: [PATCH 2/3] i2c: add support for Cypress CYUSBS234 USB-I2C
 adapter

On Mon, Sep 22, 2014 at 03:03:46PM +0530, Muthu Mani wrote:
> Adds support for USB-I2C interface of Cypress Semiconductor
> CYUSBS234 USB-Serial Bridge controller.
> 
> The read/write operation is setup using vendor command through
> control endpoint and actual data transfer happens through
> bulk in/out endpoints.
> 
> Details about the device can be found at:
> http://www.cypress.com/?rID=84126
> 
> Signed-off-by: Muthu Mani <muth@...ress.com>
> Signed-off-by: Rajaram Regupathy <rera@...ress.com>
> ---
>  drivers/i2c/busses/Kconfig         |  12 +
>  drivers/i2c/busses/Makefile        |   1 +
>  drivers/i2c/busses/i2c-cyusbs23x.c | 534 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 547 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-cyusbs23x.c
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 2ac87fa..1fdc6ec 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -848,6 +848,18 @@ config I2C_RCAR
>  
>  comment "External I2C/SMBus adapter drivers"
>  
> +config I2C_CYUSBS23X
> +        tristate "CYUSBS23x I2C adapter"
> +        depends on MFD_CYUSBS23X && USB
> +        help
> +	  Say yes if you would like to access Cypress CYUSBS23x I2C device.
> +
> +	  This driver enables the I2C interface of CYUSBS23x USB Serial Bridge
> +	  controller.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called i2c-cyusbs23x.
> +
>  config I2C_DIOLAN_U2C
>  	tristate "Diolan U2C-12 USB adapter"
>  	depends on USB
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 49bf07e..cbf28cb 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -84,6 +84,7 @@ obj-$(CONFIG_I2C_XLR)		+= i2c-xlr.o
>  obj-$(CONFIG_I2C_RCAR)		+= i2c-rcar.o
>  
>  # External I2C/SMBus adapter drivers
> +obj-$(CONFIG_I2C_CYUSBS23X)	+= i2c-cyusbs23x.o
>  obj-$(CONFIG_I2C_DIOLAN_U2C)	+= i2c-diolan-u2c.o
>  obj-$(CONFIG_I2C_PARPORT)	+= i2c-parport.o
>  obj-$(CONFIG_I2C_PARPORT_LIGHT)	+= i2c-parport-light.o
> diff --git a/drivers/i2c/busses/i2c-cyusbs23x.c b/drivers/i2c/busses/i2c-cyusbs23x.c
> new file mode 100644
> index 0000000..6fade25
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-cyusbs23x.c
> @@ -0,0 +1,534 @@
> +/*
> + * Cypress USB-Serial Bridge Controller I2C-USB adapter driver
> + *
> + * Copyright (c) 2014 Cypress Semiconductor Corporation.
> + *
> + * Author:
> + *   Rajaram Regupathy <rera@...ress.com>
> + *
> + * Additional contributors include:
> + *   Muthu Mani <muth@...ress.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.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <linux/mutex.h>
> +#include <linux/platform_device.h>
> +
> +#include <linux/usb.h>
> +#include <linux/i2c.h>
> +
> +#include <linux/mfd/cyusbs23x.h>
> +
> +#define CYUSBS23X_I2C_NAME "cyusbs23x_i2c"
> +
> +#pragma pack(1)
> +struct cyusbs_i2c_config {
> +	__u32 frequency;       /* Frequency of operation. Only valid values are
> +				  100KHz and 400KHz */

u32 -- drop the __ prefix throughout.

> +__u8 slave_addr;       /* Slave address to be used when in slave mode */
> +	bool is_msb_first;     /* Whether to transmit MSB first */

Use an explicitly sized type (e.g. u8) and not bool for this struct.

> +	bool is_master;        /* Whether block is to be configured as a master:
> +				  1 - The block functions as I2C master;
> +				  0 - The block functions as I2C slave */
> +	bool s_ignore;         /* Ignore general call in slave mode */
> +	bool clock_stretch;    /* Whether to stretch clock in case of no FIFO
> +				  availability */
> +	bool is_loopback;      /* Whether to loop back TX data to RX. Valid
> +				  only for debug purposes */
> +	__u8 reserved[6];      /* Reserved for future use */
> +};
> +#pragma pack()

Use __packed rather than pragma if at all needed.

> +
> +struct cyusbs_i2c {
> +	struct i2c_adapter i2c_adapter;
> +	struct cyusbs_i2c_config i2c_config;

Buffers used for USB (DMA) transfers needs to be allocated separately
from the containing struct.

> +
> +	bool is_stop_bit;
> +	bool is_nak_bit;
> +};
> +
> +#define CY_I2C_MODE_WRITE     1
> +#define CY_I2C_MODE_READ      0
> +
> +static int cy_i2c_get_status(struct device *d, char *buf, __u16 mode);
> +static int cy_i2c_reset(struct device *d, __u16 mode);
> +
> +static ssize_t show_i2c_read_status(struct device *d,
> +				    struct device_attribute *attr, char *buf)
> +{
> +	dev_dbg(d, "%s\n", __func__);
> +
> +	return cy_i2c_get_status(d, buf, CY_I2C_MODE_READ);
> +}
> +static DEVICE_ATTR(i2c_read_status, 0444, show_i2c_read_status, NULL);

What are these attributes used for? Can't they be handled through the
i2c-framework if at all needed?

Use DEVICE_ATTR_RO and friends rather tham DEVICE_ATTR directly.

And is it ascii data you're returning? You don't seem to null-terminate
it.

> +
> +static ssize_t show_i2c_write_status(struct device *d,
> +				     struct device_attribute *attr, char *buf)
> +{
> +	dev_dbg(d, "%s\n", __func__);
> +
> +	return cy_i2c_get_status(d, buf, CY_I2C_MODE_WRITE);
> +}
> +static DEVICE_ATTR(i2c_write_status, 0444, show_i2c_write_status, NULL);
> +
> +static ssize_t cy_i2c_read_reset(struct device *d,
> +				 struct device_attribute *attr,
> +				 const char *buf, size_t count)
> +{
> +	int ret;
> +
> +	if (((count != 1) && (count != 2 || buf[1] != '\n')) || (buf[0] != '1'))
> +		return -EINVAL;
> +
> +	dev_dbg(d, "%s\n", __func__);
> +	ret = cy_i2c_reset(d, CY_I2C_MODE_READ);
> +
> +	if (!ret)
> +		ret = count;
> +
> +	return ret;
> +}
> +static DEVICE_ATTR(i2c_read_reset, 0200, NULL, cy_i2c_read_reset);

Shouldn't this be handled from within the driver?

> +
> +static ssize_t cy_i2c_write_reset(struct device *d,
> +				  struct device_attribute *attr,
> +				  const char *buf, size_t count)
> +{
> +	int ret;
> +
> +	if (((count != 1) && (count != 2 || buf[1] != '\n')) || (buf[0] != '1'))
> +		return -EINVAL;
> +
> +	dev_dbg(d, "%s\n", __func__);
> +	ret = cy_i2c_reset(d, CY_I2C_MODE_WRITE);
> +
> +	if (!ret)
> +		ret = count;
> +
> +	return ret;
> +}
> +static DEVICE_ATTR(i2c_write_reset, 0200, NULL, cy_i2c_write_reset);
> +
> +static ssize_t show_is_stop_bit(struct device *d,
> +				struct device_attribute *attr, char *buf)
> +{
> +	struct platform_device *pdev = to_platform_device(d);
> +	struct cyusbs_i2c *cy_i2c = platform_get_drvdata(pdev);
> +
> +	return sprintf(buf, "%d\n", cy_i2c->is_stop_bit);
> +}
> +
> +static ssize_t store_is_stop_bit(struct device *d,
> +				 struct device_attribute *attr,
> +				 const char *buf, size_t count)
> +{
> +	struct platform_device *pdev = to_platform_device(d);
> +	struct cyusbs_i2c *cy_i2c = platform_get_drvdata(pdev);
> +
> +	if ((count != 1) && (count != 2 || buf[1] != '\n'))
> +		return -EINVAL;
> +
> +	if (buf[0] == '0')
> +		cy_i2c->is_stop_bit = 0;
> +	else if (buf[0] == '1')
> +		cy_i2c->is_stop_bit = 1;
> +	else
> +		return -EINVAL;
> +
> +	dev_dbg(d, "is_stop_bit=%d buf=%s\n", cy_i2c->is_stop_bit, buf);
> +
> +	return count;
> +}
> +static DEVICE_ATTR(is_stop_bit, 0644, show_is_stop_bit, store_is_stop_bit);
> +
> +static ssize_t show_is_nak_bit(struct device *d,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	struct platform_device *pdev = to_platform_device(d);
> +	struct cyusbs_i2c *cy_i2c = platform_get_drvdata(pdev);
> +
> +	return sprintf(buf, "%d\n", cy_i2c->is_nak_bit);
> +}
> +
> +static ssize_t store_is_nak_bit(struct device *d,
> +				struct device_attribute *attr,
> +				const char *buf, size_t count)
> +{
> +	struct platform_device *pdev = to_platform_device(d);
> +	struct cyusbs_i2c *cy_i2c = platform_get_drvdata(pdev);
> +
> +	if ((count != 1) && (count != 2 || buf[1] != '\n'))
> +		return -EINVAL;
> +
> +	if (buf[0] == '0')
> +		cy_i2c->is_nak_bit = 0;
> +	else if (buf[0] == '1')
> +		cy_i2c->is_nak_bit = 1;
> +	else
> +		return -EINVAL;
> +
> +	dev_dbg(d, "is_nak_bit=%d buf=%s\n", cy_i2c->is_nak_bit, buf);
> +
> +	return count;
> +}
> +static DEVICE_ATTR(is_nak_bit, 0644, show_is_nak_bit, store_is_nak_bit);
> +
> +static int cy_i2c_get_status(struct device *d, char *buf, __u16 mode)
> +{
> +	int ret;
> +	__u16 wIndex, wValue, scb_index, tmp;
> +	struct cyusbs23x *cyusbs = dev_get_drvdata(d->parent);
> +
> +	tmp = cyusbs->usb_intf->cur_altsetting->desc.bInterfaceNumber;
> +	scb_index = tmp & 0x01;
> +	wValue = ((scb_index << CY_SCB_INDEX_POS) | mode);
> +	wIndex = 0;
> +

Allocate the transfer buffer using kmalloc explicitly here and do a
memcpy if needed to make sure the buffer is always DMA-able.

> +	mutex_lock(&cyusbs->lock);
> +	ret = usb_control_msg(cyusbs->usb_dev,
> +			usb_rcvctrlpipe(cyusbs->usb_dev, 0),
> +			CY_I2C_GET_STATUS_CMD,
> +			USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
> +			wValue, wIndex, buf, 3, 2000);
> +	mutex_unlock(&cyusbs->lock);
> +
> +	dev_dbg(&cyusbs->usb_intf->dev, "%s: %02x %02x %02x\n", __func__,
> +		buf[0], buf[1], buf[2]);
> +	return ret;
> +}
> +
> +static int cy_i2c_reset(struct device *d, __u16 mode)
> +{
> +	int ret;
> +	__u16 wIndex, wValue, scb_index, tmp;
> +	struct cyusbs23x *cyusbs = dev_get_drvdata(d->parent);
> +
> +	tmp = cyusbs->usb_intf->cur_altsetting->desc.bInterfaceNumber;
> +	scb_index = tmp & 0x01;
> +	wValue = ((scb_index << CY_SCB_INDEX_POS) | mode);
> +	wIndex = 0;
> +
> +	mutex_lock(&cyusbs->lock);
> +	ret = usb_control_msg(cyusbs->usb_dev,
> +			usb_sndctrlpipe(cyusbs->usb_dev, 0),
> +			CY_I2C_RESET_CMD,
> +			USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
> +			wValue, wIndex, NULL, 0, 2000);
> +	mutex_unlock(&cyusbs->lock);
> +	dev_dbg(d, "%s: %d\n", __func__, ret);
> +	return ret;
> +}
> +
> +static int cy_get_i2c_config(struct cyusbs23x *cyusbs,
> +				struct cyusbs_i2c *cy_i2c)
> +{
> +	int ret;
> +	__u16 scb_index, tmp;
> +
> +	dev_dbg(&cyusbs->usb_intf->dev, "%s\n", __func__);
> +
> +	tmp = cyusbs->usb_intf->cur_altsetting->desc.bInterfaceNumber;
> +	scb_index = (tmp & 0x01) << CY_SCB_INDEX_POS;
> +
> +	mutex_lock(&cyusbs->lock);
> +	ret = usb_control_msg(cyusbs->usb_dev,
> +			usb_rcvctrlpipe(cyusbs->usb_dev, 0),
> +			CY_I2C_GET_CONFIG_CMD,
> +			USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
> +			scb_index, 0, &cy_i2c->i2c_config, 16, 2000);

Hardcoded length. Use proper attributes and sizeof.

> +	mutex_unlock(&cyusbs->lock);
> +
> +	dev_dbg(&cyusbs->usb_intf->dev, "%s: %d, 0x%02x, %d, %d, %d, %d, %d\n",
> +		__func__, cy_i2c->i2c_config.frequency,
> +		cy_i2c->i2c_config.slave_addr,
> +		cy_i2c->i2c_config.is_msb_first,
> +		cy_i2c->i2c_config.is_master,
> +		cy_i2c->i2c_config.s_ignore,
> +		cy_i2c->i2c_config.clock_stretch,
> +		cy_i2c->i2c_config.is_loopback);
> +	return ret;
> +}
> +
> +static int cy_i2c_set_data_config(struct cyusbs23x *cyusbs,
> +				  struct cyusbs_i2c *cy_i2c, __u16 slave_addr,
> +				  __u16 length, __u8 command)
> +{
> +	int ret;
> +	__u16 wIndex, wValue;
> +	__u16 scb_index, tmp;
> +
> +	dev_dbg(&cyusbs->usb_intf->dev, "%s\n", __func__);
> +
> +	tmp = cyusbs->usb_intf->cur_altsetting->desc.bInterfaceNumber;
> +	scb_index = (tmp & 0x01) << 7;
> +	slave_addr = (slave_addr & 0x7F) | scb_index;
> +	wValue = cy_i2c->is_stop_bit | cy_i2c->is_nak_bit << 1;
> +	wValue |= (slave_addr << 8);
> +	wIndex = length;
> +
> +	dev_dbg(&cyusbs->usb_intf->dev,
> +		"%s, cmd=0x%x,val=0x%x,idx=0x%x\n",
> +		__func__, command, wValue, wIndex);
> +
> +	ret = usb_control_msg(cyusbs->usb_dev,
> +		usb_sndctrlpipe(cyusbs->usb_dev, 0),
> +		command, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
> +		wValue, wIndex, NULL, 0, 2000);
> +
> +	return ret;
> +}
> +
> +static int cy_i2c_read(struct cyusbs23x *cyusbs, struct i2c_msg *msgs)
> +{
> +	int ret, actual_read_len = 0;
> +
> +	dev_dbg(&cyusbs->usb_intf->dev, "%s\n", __func__);
> +
> +	ret = usb_bulk_msg(cyusbs->usb_dev,
> +		usb_rcvbulkpipe(cyusbs->usb_dev, cyusbs->bulk_in_ep_num),
> +		msgs[0].buf,
> +		msgs[0].len,
> +		&actual_read_len, 5000);
> +
> +	if (ret)
> +		dev_dbg(&cyusbs->usb_intf->dev,
> +			"read %d/%d returned %d\n",
> +			actual_read_len, msgs[0].len, ret);
> +
> +	return ret;
> +}
> +
> +static int cy_i2c_write(struct cyusbs23x *cyusbs, struct i2c_msg *msgs)
> +{
> +	int ret, actual_write_len = 0;
> +
> +	dev_dbg(&cyusbs->usb_intf->dev, "%s\n", __func__);
> +
> +	ret = usb_bulk_msg(cyusbs->usb_dev,
> +		usb_sndbulkpipe(cyusbs->usb_dev, cyusbs->bulk_out_ep_num),
> +		msgs[0].buf,
> +		msgs[0].len,
> +		&actual_write_len, 5000);
> +
> +	if (ret)
> +		dev_dbg(&cyusbs->usb_intf->dev,
> +			"write %d/%d returned %d\n",
> +			actual_write_len, msgs[0].len, ret);
> +
> +	return ret;
> +}
> +
> +static int cy_i2c_xfer(struct i2c_adapter *adapter,
> +		       struct i2c_msg *msgs, int num)
> +{
> +	int ret = 0;
> +	struct cyusbs_i2c *cy_i2c;
> +	struct cyusbs23x *cyusbs = (struct cyusbs23x *)adapter->algo_data;
> +
> +	dev_dbg(&adapter->dev, "%s\n", __func__);
> +
> +	if (num > 1) {
> +		dev_err(&adapter->dev, "i2c_msg number is > 1\n");
> +		return -EIO;
> +	}

Why not handle multiple messages?

> +
> +	cy_i2c = container_of(adapter, struct cyusbs_i2c, i2c_adapter);
> +
> +	mutex_lock(&cyusbs->lock);
> +	if (msgs[0].flags & I2C_M_RD) {
> +		dev_dbg(&adapter->dev,
> +			"I2C read requested for addr 0x%02x, data length %d\n",
> +			msgs[0].addr, msgs[0].len);
> +
> +		ret = cy_i2c_set_data_config(cyusbs, cy_i2c, msgs[0].addr,
> +				msgs[0].len, CY_I2C_READ_CMD);
> +
> +		if (ret < 0) {
> +			dev_err(&adapter->dev,
> +				"Set Config (read) failed with %d\n", ret);
> +			goto io_error;
> +		}
> +
> +		ret = cy_i2c_read(cyusbs, msgs);
> +		if (ret) {
> +			dev_err(&adapter->dev,
> +				"Read failed with error code %d\n", ret);
> +			goto io_error;
> +		}
> +	} else {
> +		dev_dbg(&adapter->dev,
> +			"I2C write requested for addr 0x%02x, data length %d\n",
> +			msgs[0].addr, msgs[0].len);
> +
> +		ret = cy_i2c_set_data_config(cyusbs, cy_i2c, msgs[0].addr,
> +				msgs[0].len, CY_I2C_WRITE_CMD);
> +
> +		if (ret < 0) {
> +			dev_err(&adapter->dev,
> +			"Set Config (write) failed with %d\n", ret);
> +			goto io_error;
> +		}
> +
> +		ret = cy_i2c_write(cyusbs, msgs);
> +		if (ret) {
> +			dev_err(&adapter->dev,
> +				"Write failed with error code %d\n", ret);
> +			goto io_error;
> +		}
> +	}
> +	mutex_unlock(&cyusbs->lock);
> +	return ret;
> +
> +io_error:
> +	mutex_unlock(&cyusbs->lock);
> +	return ret;
> +}
> +
> +static u32 cy_i2c_func(struct i2c_adapter *adapter)
> +{
> +	dev_dbg(&adapter->dev, "%s\n", __func__);
> +
> +	return I2C_FUNC_I2C;
> +}
> +
> +static const struct i2c_algorithm i2c_cyusbs23x_algorithm = {
> +	.master_xfer	= cy_i2c_xfer,
> +	.functionality	= cy_i2c_func,
> +};
> +
> +static int cyusbs23x_i2c_probe(struct platform_device *pdev)
> +{
> +	struct cyusbs23x *cyusbs;
> +	struct cyusbs_i2c *cy_i2c;
> +	int ret = 0;
> +
> +	dev_dbg(&pdev->dev, "%s\n", __func__);
> +
> +	cyusbs = dev_get_drvdata(pdev->dev.parent);
> +
> +	cy_i2c = devm_kzalloc(&pdev->dev, sizeof(*cy_i2c), GFP_KERNEL);
> +	if (cy_i2c == NULL)
> +		return -ENOMEM;
> +
> +	cy_i2c->is_stop_bit = 1;
> +	cy_i2c->is_nak_bit = 1;
> +
> +	cy_i2c->i2c_adapter.owner = THIS_MODULE;
> +	cy_i2c->i2c_adapter.class = I2C_CLASS_HWMON;
> +	cy_i2c->i2c_adapter.algo = &i2c_cyusbs23x_algorithm;
> +	cy_i2c->i2c_adapter.algo_data = cyusbs;
> +	snprintf(cy_i2c->i2c_adapter.name, sizeof(CYUSBS23X_I2C_NAME),
> +			CYUSBS23X_I2C_NAME);
> +	cy_i2c->i2c_adapter.dev.parent = &pdev->dev;
> +
> +	ret = device_create_file(&pdev->dev, &dev_attr_i2c_read_status);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"error in adding i2c_read_status\n");
> +		goto error;
> +	}
> +	ret = device_create_file(&pdev->dev, &dev_attr_i2c_write_status);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"error in adding i2c_write_status\n");
> +		goto error;
> +	}
> +
> +	ret = device_create_file(&pdev->dev, &dev_attr_i2c_read_reset);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"error in adding i2c_read_reset\n");
> +		goto error;
> +	}
> +	ret = device_create_file(&pdev->dev, &dev_attr_i2c_write_reset);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"error in adding i2c_write_reset\n");
> +		goto error;
> +	}
> +
> +	ret = device_create_file(&pdev->dev, &dev_attr_is_nak_bit);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"error in adding is_nak_bit\n");
> +		goto error;
> +	}
> +	ret = device_create_file(&pdev->dev, &dev_attr_is_stop_bit);
> +	if (ret) {
> +		dev_err(&pdev->dev,
> +			"error in adding is_stop_bit\n");
> +		goto error;
> +	}

If really needed, these attributes should be attributes of the i2c
adapter and not the platform device. And use attribute groups rather
than device_create_file to avoid racing with userspace.

> +
> +	ret = cy_get_i2c_config(cyusbs, cy_i2c);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "error to get i2c config\n");
> +		goto error;

You never release the attribute files created above in these error
paths.

> +	}
> +
> +	if (!cy_i2c->i2c_config.is_master) {
> +		ret = -EIO;
> +		dev_err(&pdev->dev, "not an I2C master\n");

What is returned here if the adapter is in for example SPI mode?

> +		goto error;
> +	}
> +
> +	ret = i2c_add_adapter(&cy_i2c->i2c_adapter);
> +	if (ret != 0) {
> +		dev_err(&pdev->dev, "failed to add i2c adapter\n");
> +		goto error;
> +	}
> +
> +	platform_set_drvdata(pdev, cy_i2c);
> +
> +	dev_dbg(&pdev->dev, "added I2C adapter\n");
> +	return 0;
> +
> +error:
> +	dev_dbg(&pdev->dev, "error occured %d\n", ret);
> +	return ret;
> +}
> +
> +static int cyusbs23x_i2c_remove(struct platform_device *pdev)
> +{
> +	struct cyusbs_i2c *cy_i2c = platform_get_drvdata(pdev);
> +
> +	dev_dbg(&pdev->dev, "%s\n", __func__);
> +
> +	i2c_del_adapter(&cy_i2c->i2c_adapter);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver cyusbs23x_i2c_driver = {
> +	.driver.name	= "cyusbs23x-i2c",
> +	.driver.owner	= THIS_MODULE,
> +	.probe		= cyusbs23x_i2c_probe,
> +	.remove		= cyusbs23x_i2c_remove,
> +};
> +
> +static int __init cyusbs23x_i2c_init(void)
> +{
> +	return platform_driver_register(&cyusbs23x_i2c_driver);
> +}
> +subsys_initcall(cyusbs23x_i2c_init);
> +
> +static void __exit cyusbs23x_i2c_exit(void)
> +{
> +	platform_driver_unregister(&cyusbs23x_i2c_driver);
> +}
> +module_exit(cyusbs23x_i2c_exit);

Use module_platform_driver

> +
> +MODULE_AUTHOR("Rajaram Regupathy <rera@...ress.com>");
> +MODULE_AUTHOR("Muthu Mani <muth@...ress.com>");
> +MODULE_DESCRIPTION("i2c-cyusbs23x driver v0.1");

This is not a description.

Drop the version number as the kernel version is what matters.

> +MODULE_LICENSE("GPL");

GPL v2 only?

> +MODULE_ALIAS("platform:cyusbs23x-i2c");

Johan
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