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Date:	Wed, 8 Jan 2014 22:39:33 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Laszlo Papp <lpapp@....org>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mfd: MAX6650/6651 support

> MAX6650/MAX6651 chip is a multi-function device with I2C busses. The
> chip includes fan-speed regulators and monitors, GPIO, and alarm.
> 
> This patch is an initial release of a MAX6650/6651 MFD driver that
> supports to enable the chip with its primary I2C bus that will connect
> the hwmon, and then the gpio devices for now.
> 
> Signed-off-by: Laszlo Papp <lpapp@....org>
> ---
>  drivers/mfd/Kconfig                 |  11 +++
>  drivers/mfd/Makefile                |   1 +
>  drivers/mfd/max6651.c               | 132 ++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/max6651-private.h |  53 +++++++++++++++
>  4 files changed, 197 insertions(+)
>  create mode 100644 drivers/mfd/max6651.c
>  create mode 100644 include/linux/mfd/max6651-private.h
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index dd67158..706c4e5 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -321,6 +321,17 @@ config MFD_88PM860X
>  	  select individual components like voltage regulators, RTC and
>  	  battery-charger under the corresponding menus.
>  
> +config MFD_MAX6651
> +	bool "Maxim Semiconductor MAX6651 Support"
> +	depends on I2C=y
> +	select MFD_CORE
> +	select IRQ_DOMAIN

Why have you selected IRQ_DOMAIN?

> +#include <linux/device.h>
> +#include <linux/delay.h>
> +#include <linux/input.h>
> +#include <linux/interrupt.h>
> +#include <linux/mfd/core.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/i2c.h>

Are you sure all these are used? I'm pretty sure some of them are
not. Only add headers if you require them. Try not to copy and paste
stuff you don't need.

> +#include <linux/mfd/max6651-private.h>
> +
> +static struct mfd_cell max6651_devs[] = {
> +    { .name = "max6651-gpio", },
> +    { .name = "max6650", },

It would be nice to have a comment here to indicate that this is a
hwmon driver. If you're planning to add support for the MAX6651 to
this existing driver, also consider renaming it to "max665x".

> +};
> +
> +int max6651_read_reg(struct i2c_client *i2c, u8 reg, u8 *dest)
> +{

Probably best to use Regmap instead.

regmap_i2c_read()

> +    struct max6651_dev *max6651 = i2c_get_clientdata(i2c);
> +    int ret;

Always use 8 char tabs for kernel code.

> +    mutex_lock(&max6651->iolock);
> +    ret = i2c_smbus_read_byte_data(i2c, reg);
> +    mutex_unlock(&max6651->iolock);
> +    if (ret < 0)
> +        return ret;
> +
> +    ret &= 0xff;
> +    *dest = ret;

*dest = ret & 0xff is clear enough.

> +    return 0;
> +}
> +EXPORT_SYMBOL_GPL(max6651_read_reg);
> +
> +int max6651_write_reg(struct i2c_client *i2c, u8 reg, u8 value)
> +{
> +    struct max6651_dev *max6651 = i2c_get_clientdata(i2c);
> +    int ret;

Same here.

regmap_i2c_write()

> +    mutex_lock(&max6651->iolock);
> +    ret = i2c_smbus_write_byte_data(i2c, reg, value);
> +    mutex_unlock(&max6651->iolock);
> +    return ret;
> +}
> +EXPORT_SYMBOL_GPL(max6651_write_reg);
> +
> +static int max6651_i2c_probe(struct i2c_client *i2c,
> +			    const struct i2c_device_id *id)
> +{
> +	struct max6651_dev *max6651;
> +	int ret = 0;

Why are you initialising ret?

> +	max6651 = kzalloc(sizeof(struct max6651_dev), GFP_KERNEL);

Use managed resources devm_*.

s/sizeof(struct max6651_dev)/sizeof(*max6651)/

> +	if (max6651 == NULL)

if (!max6651)

> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(i2c, max6651);
> +	max6651->dev = &i2c->dev;
> +
> +	mutex_init(&max6651->iolock);
> +
> +	ret = mfd_add_devices(max6651->dev, -1, max6651_devs,
> +			ARRAY_SIZE(max6651_devs),
> +			NULL, 0, NULL);
> +
> +	if (ret < 0) {
> +        dev_err(max6651->dev, "cannot add mfd cells\n");

Are you trying to add cells or register devices?

> +		goto err_mfd;
> +    }
> +
> +	return ret;
> +
> +err_mfd:
> +	mfd_remove_devices(max6651->dev);

If mfd_add_devices() failed, you don't need to remove them.

> +	kfree(max6651);

If you use managed resources you don't need this.

> +	return ret;
> +}
> +
> +static int max6651_i2c_remove(struct i2c_client *i2c)
> +{
> +    struct max6651_dev *max6651 = i2c_get_clientdata(i2c);
> +
> +    mfd_remove_devices(max6651->dev);

In this case you would normally need to kfree() here, but if you use
managed resources you won't have to.

> +    return 0;
> +}
> +
> +static const struct i2c_device_id max6651_i2c_id[] = {
> +    { "max6650", TYPE_MAX6650 },
> +    { "max6651", TYPE_MAX6651 },

So were're registering the max6650 from here too?

If so, then you need to change the name of the file.

> +    { }

{},

> +};
> +MODULE_DEVICE_TABLE(i2c, max6651_i2c_id);
> +
> +static struct i2c_driver max6651_i2c_driver = {
> +    .driver = {
> +           .name = "max6651",
> +           .owner = THIS_MODULE,
> +    },
> +    .probe = max6651_i2c_probe,
> +    .remove = max6651_i2c_remove,
> +    .id_table = max6651_i2c_id,
> +};

Remove from here ------

> +static int __init max6651_i2c_init(void)
> +{
> +    return i2c_add_driver(&max6651_i2c_driver);
> +}
> +/* init early so consumer devices can complete system boot */

I don't think this is required.

> +subsys_initcall(max6651_i2c_init);
> +
> +static void __exit max6651_i2c_exit(void)
> +{
> +    i2c_del_driver(&max6651_i2c_driver);
> +}
> +module_exit(max6651_i2c_exit);

To here -----

 and replace with one line:

  module_i2c_driver()

<snip>

> +#ifndef __LINUX_MFD_MAX6651_PRIVATE_H
> +#define __LINUX_MFD_MAX6651_PRIVATE_H
> +
> +#include <linux/i2c.h>
> +#include <linux/export.h>

Why is this in here?

> +#include <linux/irqdomain.h>

And this?

> +struct max6651_dev {
> +    struct device *dev;
> +    struct mutex iolock;
> +
> +    struct i2c_client *i2c;

Is this used?

> +	int type;

Or this?

> +};
> +
> +enum max6651_types {
> +	TYPE_MAX6650,
> +	TYPE_MAX6651,
> +};

What are you using these for?

> +extern int max6651_read_reg(struct i2c_client *i2c, u8 reg, u8 *dest);
> +extern int max6651_write_reg(struct i2c_client *i2c, u8 reg, u8 value);

regmap_i2c_read()
regmap_i2c_write()

> +#endif

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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