Re: [PATCH 1/3] drivers/mfd/menf21bmc: introduce MEN 14F021P00 BMC MFD Core driver

[Guenter Roeck <linux@roeck-us.net>]

On 05/19/2014 05:43 AM, Andreas Werner wrote:
> aOn Sat, May 17, 2014 at 08:47:42AM -0700, Guenter Roeck wrote:
>> On 05/16/2014 09:37 AM, Andreas Werner wrote:
>>> The MEN 14F021P00 Board Management Controller provides an
>>> I2C interface to the host to access the feature implemented in the BMC.
>>> The BMC is a PIC Microntroller assembled on CPCI Card from MEN Mikroelektronik
>>> and on a few Box/Display Computer.
>>>
>>> Added MFD Core driver, supporting the I2C communication to the device.
>>>
>>> The MFD driver currently supports the following features:
>>> 	- Watchdog
>>> 	- LEDs
>>>
>>> Signed-off-by: Andreas Werner <andreas.werner@men.de>
>>> ---
>>>   drivers/mfd/Kconfig           |  12 +++
>>>   drivers/mfd/Makefile          |   1 +
>>>   drivers/mfd/menf21bmc.c       | 193 ++++++++++++++++++++++++++++++++++++++++++
>>>   include/linux/mfd/menf21bmc.h |  32 +++++++
>>>   4 files changed, 238 insertions(+)
>>>   create mode 100644 drivers/mfd/menf21bmc.c
>>>   create mode 100644 include/linux/mfd/menf21bmc.h
>>>
>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>>> index ab5a43c..7c2e8d2 100644
>>> --- a/drivers/mfd/Kconfig
>>> +++ b/drivers/mfd/Kconfig
>>> @@ -427,6 +427,18 @@ config MFD_MAX8998
>>>   	  additional drivers must be enabled in order to use the functionality
>>>   	  of the device.
>>>
>>> +config MFD_MENF21BMC
>>> +	tristate "MEN 14F021P00 Board Management Controller Support"
>>> +	depends on I2C=y
>>> +	select MFD_CORE
>>> +	help
>>> +	  Say yes here to add support for the MEN 14F021P00 BMC
>>> +	  which is a Board Management Controller connected to the I2C bus.
>>> +	  This driver provides common support for accessing the devices;
>>> +	  additional drivers must be enabled in order to use the
>>> +	  functionality of the BMC device.
>>> +
>>> +
>>>   config EZX_PCAP
>>>   	bool "Motorola EZXPCAP Support"
>>>   	depends on SPI_MASTER
>>> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
>>> index 5913208..8f2be38 100644
>>> --- a/drivers/mfd/Makefile
>>> +++ b/drivers/mfd/Makefile
>>> @@ -167,3 +167,4 @@ obj-$(CONFIG_MFD_AS3711)	+= as3711.o
>>>   obj-$(CONFIG_MFD_AS3722)	+= as3722.o
>>>   obj-$(CONFIG_MFD_STW481X)	+= stw481x.o
>>>   obj-$(CONFIG_MFD_IPAQ_MICRO)	+= ipaq-micro.o
>>> +obj-$(CONFIG_MFD_MENF21BMC)	+= menf21bmc.o
>>> diff --git a/drivers/mfd/menf21bmc.c b/drivers/mfd/menf21bmc.c
>>> new file mode 100644
>>> index 0000000..77de1a8
>>> --- /dev/null
>>> +++ b/drivers/mfd/menf21bmc.c
>>> @@ -0,0 +1,193 @@
>>> +/*
>>> + *  MEN 14F021P00 Board Management Controller (BMC) MFD Core Driver.
>>> + *
>>> + *  Copyright (C) 2014 MEN Mikro Elektronik Nuernberg GmbH
>>> + *  Author: Andreas Werner <andreas.werner@men.de>
>>> + *  All rights reserved.
>>> + *
>>> + *  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;  either version 2 of the  License, or (at your
>>> + *  option) any later version.
>>> + *
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/device.h>
>>> +#include <linux/module.h>
>>> +#include <linux/i2c.h>
>>> +#include <linux/mfd/core.h>
>>> +#include <linux/mfd/menf21bmc.h>
>>> +
>>> +#define BMC_CMD_REV_MAJOR	0x80
>>> +#define BMC_CMD_REV_MINOR	0x81
>>> +#define BMC_CMD_REV_MAIN	0x82
>>> +#define BMC_CMD_REV_BUILD	0x83
>>> +#define BMC_CMD_REV_VERI	0x84
>>> +
>>> +static struct mfd_cell menf21bmc_cell[] = {
>>> +	{
>>> +		.name = "menf21bmc_wd",
>>> +	},
>>> +	{
>>> +		.name = "menf21bmc_led",
>>> +	},
>>> +};
>>> +
>>> +static int
>>> +menf21bmc_read_byte_data(struct i2c_client *client, u8 reg, uint8_t *val)
>>> +{
>>> +	int ret;
>>> +	struct menf21bmc *data = i2c_get_clientdata(client);
>>> +
>>> +	mutex_lock(&data->lock);
>>> +	ret = i2c_smbus_read_byte_data(client, reg);
>>> +	mutex_unlock(&data->lock);
>>> +
>>> +	if (ret < 0) {
>>> +		dev_err(&client->dev, "failed to read byte at 0x%02x\n", reg);
>>> +		return ret;
>>> +	}
>>> +
>>> +	*val = (uint8_t)ret;
>>> +
>>> +	return 0;
>>> +}
>>> +
>> I personally would prefer if you would retain the original API, which returns both value
>> and error code as return value. I don't see the benefit of changing the API as you did -
>> it just complicates the code.
>>
>> Thanks,
>> Guenter
>>
> I think it is ok for a wrapper like this because it does not really change an API because
> it is menf21bmc related.
>
> I did the same in rtc-rx8581, and it was already done in rtc_ds1307.c.
>
> I personally prefer this way because the return of the function and the return
> value of the i2c_smbus_read - which is the value read from the device - are seperated.
>
> If it is a no go for the mfd/wdt core i can change it back to the original i2c_smbus API.
> If it is ok on your side for a wrapper like this, we can let it as it is.
>

Not my call to make; depends on the mfd maintainer. I would not accept it, as I see it
as unnecessary, adding complexity, and pointless. Sure, you can always find examples
for everything somewhere in the kernel, but that doesn't make it better.

Guenter