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Date:	Fri, 08 Aug 2014 07:17:01 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Andreas Werner <andreas.werner@....de>
CC:	Wim Van Sebroeck <wim@...ana.be>, Bryan Wu <cooloney@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	"rpurdie@...ys.net" <rpurdie@...ys.net>,
	Linux LED Subsystem <linux-leds@...r.kernel.org>,
	linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v3 3/3] drivers/leds/leds-menf21bmc: introduce MEN 14F021P00
 BMC LED driver

On 08/08/2014 12:49 AM, Andreas Werner wrote:
> On Wed, Jul 30, 2014 at 06:57:46AM -0700, Guenter Roeck wrote:
>> On 07/30/2014 01:08 AM, Andreas Werner wrote:
>>> On Tue, Jul 29, 2014 at 02:47:08PM -0700, Guenter Roeck wrote:
>>>> On 07/29/2014 02:12 PM, Wim Van Sebroeck wrote:
>>>>> Hi Andreas,
>>>>>
>>>>>> aOn Thu, Jul 24, 2014 at 03:00:09PM -0700, Bryan Wu wrote:
>>>>>>> On Thu, Jul 17, 2014 at 6:18 AM, Andreas Werner <andreas.werner@....de> wrote:
>>>>>>>> Added driver to support the 14F021P00 BMC LEDs.
>>>>>>>> The BMC is a Board Management Controll include four LEDs which
>>>>>>>> can be switched on and off.
>>>>>>>>
>>>>>>>> This driver use the I2C interface to the BMC using the menf21bmc MFD Core driver.
>>>>>>>>
>>>>>>>> Signed-off-by: Andreas Werner <andreas.werner@....de>
>>>>>>>> ---
>>>>>>>>   drivers/leds/Kconfig          |   6 ++
>>>>>>>>   drivers/leds/Makefile         |   1 +
>>>>>>>>   drivers/leds/leds-menf21bmc.c | 134 ++++++++++++++++++++++++++++++++++++++++++
>>>>>>>>   3 files changed, 141 insertions(+)
>>>>>>>>   create mode 100644 drivers/leds/leds-menf21bmc.c
>>>>>>>>
>>>>>>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>>>>>>> index 27cf0cd..d38ff3f 100644
>>>>>>>> --- a/drivers/leds/Kconfig
>>>>>>>> +++ b/drivers/leds/Kconfig
>>>>>>>> @@ -458,6 +458,12 @@ config LEDS_OT200
>>>>>>>>            This option enables support for the LEDs on the Bachmann OT200.
>>>>>>>>            Say Y to enable LEDs on the Bachmann OT200.
>>>>>>>>
>>>>>>>> +config LEDS_MENF21BMC
>>>>>>>> +       tristate "LED support for the MEN 14F021P00 BMC"
>>>>>>>> +       depends on LEDS_CLASS && MFD_MENF21BMC
>>>>>>>
>>>>>>> I think it also depends on I2C.
>>>>>>
>>>>>> Yes you are right.
>>>>>>
>>>>>>>
>>>>>>>> +       help
>>>>>>>> +         Say Y here to include support for the MEN 14F021P00 BMC LEDs.
>>>>>>>> +
>>>>>>>>   comment "LED driver for blink(1) USB RGB LED is under Special HID drivers (HID_THINGM)"
>>>>>>>>
>>>>>>>>   config LEDS_BLINKM
>>>>>>>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>>>>>>>> index 3c03666..cadc433 100644
>>>>>>>> --- a/drivers/leds/Makefile
>>>>>>>> +++ b/drivers/leds/Makefile
>>>>>>>> @@ -53,6 +53,7 @@ obj-$(CONFIG_LEDS_MAX8997)            += leds-max8997.o
>>>>>>>>   obj-$(CONFIG_LEDS_LM355x)              += leds-lm355x.o
>>>>>>>>   obj-$(CONFIG_LEDS_BLINKM)              += leds-blinkm.o
>>>>>>>>   obj-$(CONFIG_LEDS_VERSATILE)           += leds-versatile.o
>>>>>>>> +obj-$(CONFIG_LEDS_MENF21BMC)           += leds-menf21bmc.o
>>>>>>>>
>>>>>>>>   # LED SPI Drivers
>>>>>>>>   obj-$(CONFIG_LEDS_DAC124S085)          += leds-dac124s085.o
>>>>>>>> diff --git a/drivers/leds/leds-menf21bmc.c b/drivers/leds/leds-menf21bmc.c
>>>>>>>> new file mode 100644
>>>>>>>> index 0000000..5eaa119
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/drivers/leds/leds-menf21bmc.c
>>>>>>>> @@ -0,0 +1,134 @@
>>>>>>>> +/*
>>>>>>>> + *  MEN 14F021P00 Board Management Controller (BMC) LEDs Driver.
>>>>>>>> + *
>>>>>>>> + *  This is the core LED driver of the MEN 14F021P00 BMC.
>>>>>>>> + *  There are four LEDs available which can be switched on and off.
>>>>>>>> + *  STATUS LED, HOT SWAP LED, USER LED 1, USER LED 2
>>>>>>>> + *
>>>>>>>> + *  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/module.h>
>>>>>>>> +#include <linux/kernel.h>
>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>> +#include <linux/leds.h>
>>>>>>>> +#include <linux/i2c.h>
>>>>>>>> +
>>>>>>>> +#define BMC_CMD_LED_GET_SET    0xA0
>>>>>>>> +#define BMC_BIT_LED_STATUS     BIT(0)
>>>>>>>> +#define BMC_BIT_LED_HOTSWAP    BIT(1)
>>>>>>>> +#define BMC_BIT_LED_USER1      BIT(2)
>>>>>>>> +#define BMC_BIT_LED_USER2      BIT(3)
>>>>>>>> +
>>>>>>>> +struct menf21bmc_led {
>>>>>>>> +       struct led_classdev cdev;
>>>>>>>> +       u8 led_bit;
>>>>>>>> +       const char *name;
>>>>>>>> +       struct i2c_client *i2c_client;
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +static struct menf21bmc_led leds[] = {
>>>>>>>> +       {
>>>>>>>> +               .name = "menf21bmc:led_status",
>>>>>>>> +               .led_bit = BMC_BIT_LED_STATUS,
>>>>>>>> +       },
>>>>>>>> +       {
>>>>>>>> +               .name = "menf21bmc:led_hotswap",
>>>>>>>> +               .led_bit = BMC_BIT_LED_HOTSWAP,
>>>>>>>> +       },
>>>>>>>> +       {
>>>>>>>> +               .name = "menf21bmc:led_user1",
>>>>>>>> +               .led_bit = BMC_BIT_LED_USER1,
>>>>>>>> +       },
>>>>>>>> +       {
>>>>>>>> +               .name = "menf21bmc:led_user2",
>>>>>>>> +               .led_bit = BMC_BIT_LED_USER2,
>>>>>>>> +       }
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +static DEFINE_MUTEX(led_lock);
>>>>>>>> +
>>>>>>>> +static void
>>>>>>>> +menf21bmc_led_set(struct led_classdev *led_cdev, enum led_brightness value)
>>>>>>>> +{
>>>>>>>> +       int led_val;
>>>>>>>> +       struct menf21bmc_led *led = container_of(led_cdev,
>>>>>>>> +                                       struct menf21bmc_led, cdev);
>>>>>>>> +
>>>>>>>> +       mutex_lock(&led_lock);
>>>>>>>> +       led_val = i2c_smbus_read_byte_data(led->i2c_client,
>>>>>>>> +                                               BMC_CMD_LED_GET_SET);
>>>>>>>> +       if (led_val < 0)
>>>>>>>> +               goto err_out;
>>>>>>>> +
>>>>>>>> +       if (value == LED_OFF)
>>>>>>>> +               led_val &= ~led->led_bit;
>>>>>>>> +       else
>>>>>>>> +               led_val |= led->led_bit;
>>>>>>>> +
>>>>>>>> +       i2c_smbus_write_byte_data(led->i2c_client,
>>>>>>>> +                                       BMC_CMD_LED_GET_SET, led_val);
>>>>>>>> +err_out:
>>>>>>>> +       mutex_unlock(&led_lock);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static int menf21bmc_led_probe(struct platform_device *pdev)
>>>>>>>> +{
>>>>>>>> +       int i;
>>>>>>>> +       int ret;
>>>>>>>> +       struct i2c_client *i2c_client = to_i2c_client(pdev->dev.parent);
>>>>>>>> +
>>>>>>>> +       for (i = 0; i < ARRAY_SIZE(leds); i++) {
>>>>>>>> +               leds[i].cdev.name = leds[i].name;
>>>>>>>> +               leds[i].cdev.brightness_set = menf21bmc_led_set;
>>>>>>>> +               leds[i].i2c_client = i2c_client;
>>>>>>>> +               ret = led_classdev_register(&pdev->dev, &leds[i].cdev);
>>>>>>>> +               if (ret < 0)
>>>>>>>> +                       goto err_free_leds;
>>>>>>>> +       }
>>>>>>>> +       dev_info(&pdev->dev, "MEN 140F21P00 BMC LED device enabled\n");
>>>>>>>> +
>>>>>>>> +       return 0;
>>>>>>>> +
>>>>>>>> +err_free_leds:
>>>>>>>> +       dev_err(&pdev->dev, "failed to register LED device\n");
>>>>>>>> +
>>>>>>>> +       for (i = i - 1; i >= 0; i--)
>>>>>>>> +               led_classdev_unregister(&leds[i].cdev);
>>>>>>>> +
>>>>>>>> +       return ret;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static int menf21bmc_led_remove(struct platform_device *pdev)
>>>>>>>> +{
>>>>>>>> +       int i;
>>>>>>>> +
>>>>>>>> +       for (i = 0; i < ARRAY_SIZE(leds); i++)
>>>>>>>> +               led_classdev_unregister(&leds[i].cdev);
>>>>>>>> +
>>>>>>>> +       return 0;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static struct platform_driver menf21bmc_led = {
>>>>>>>> +       .probe          = menf21bmc_led_probe,
>>>>>>>> +       .remove         = menf21bmc_led_remove,
>>>>>>>> +       .driver         = {
>>>>>>>> +               .name           = "menf21bmc_led",
>>>>>>>> +               .owner          = THIS_MODULE,
>>>>>>>> +       },
>>>>>>>> +};
>>>>>>>> +
>>>>>>>
>>>>>>> This is not a normal platform driver, it should be a I2C driver.
>>>>>>>
>>>>>>>> +module_platform_driver(menf21bmc_led);
>>>>>>>
>>>>>>> So please move to use module_i2c_driver.
>>>>>>
>>>>>> Ok, but then I have to change that in the watchdog driver too, which
>>>>>> is quite the same as here.
>>>>>>
>>>>>> Lee, Guenther what do you think regarding the watchdog driver?
>>>>>
>>>>> If the watchdog part is indeed also i2c alike device then the watchdog part should also be an i2c driver...
>>>>>
>>>>
>>>> Isn't this all the same chip ? If so, there should be only one i2c driver.
>>>> Unless the i2c access is too complicated, it might make sense to use regmap
>>>> to access the chip, and pass the regmap pointer to the mfd slave drivers
>>>> to handle the actual communication with the chip.
>>>>
>>>> Guenter
>>>>
>>>
>>> Yes this is all the same chip which has different features like LEDs and Watchdog.
>>> This is why the mfd is the i2c_driver which instantiates the slave devices which
>>> are platform drivers.
>>>
>>> Is that not the normal way to handle those device?
>>> Is it really necessary to handle this to regmap?
>>>
>>
>> Not really sure if 'necessary' is the right term, it is just convenient.
>> Regmap takes care of register caching, for example, so you would not have to
>> re-read register values again and again from the chip just to modify a bit
>> of a register.
>> You can pass the regmap pointer in the platform data, or you can pass the
>> pointer to the i2c client. Using regmap makes the client driver independent
>> of the i2c subsystem. The one thing you can _not_ do is to declare the client
>> drivers to be i2c drivers.
>>
>> Guenter
>>
> I've checked out the regmap and it really sounds good.
> Before I will made those changes which is almost a complete replacement
> of the interface, i would like to know exactly why the slaves are no platform
> devices.
>
Did I say that ?

Guenter

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