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

[Andreas Werner]

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@xxxxxx>
> >---
> >  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@xxxxxx>
> >+ *  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.

Thanks
Andy

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