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

[Lee Jones]

On Mon, 19 May 2014, Guenter Roeck wrote:

> 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@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.
> >
> 
> 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.

I'm inclined to agree with Guenter, this patch is just noise.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
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