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Date: Mon, 19 May 2014 06:23:32 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Andreas Werner <andreas.werner@....de>
CC: linux-kernel@...r.kernel.org, sameo@...ux.intel.com,
lee.jones@...aro.org, wim@...ana.be,
linux-watchdog@...r.kernel.org, cooloney@...il.com,
rpurdie@...ys.net, linux-leds@...r.kernel.org,
johannes.thumshirn@....de, thomas.schnuerer@....de,
wernerandy@....de
Subject: Re: [PATCH 1/3] drivers/mfd/menf21bmc: introduce MEN 14F021P00 BMC
MFD Core driver
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@....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@....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
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