[PATCH 1/2] hwmon: add generic GPIO fan driver

Simon Guinot
2010-10-18T20:36:10Z

Hi Guenter,

Thanks for your review.

On Mon, Oct 18, 2010 at 09:08:30AM -0700, Guenter Roeck wrote:
> On Sun, Oct 17, 2010 at 11:50:11AM -0400, Simon Guinot wrote:
> > From: Simon Guinot <sguinot@lacie.com>
> >
> > This patch adds hwmon support for the GPIO connected fan.
> >
> > Platform specific informations as GPIO pinout and speed conversion array
> > (rpm from/to GPIO value) are passed to the driver via platform_data.
> >
> > Signed-off-by: Simon Guinot <sguinot@lacie.com>
>
> Hi Simon,
>
> good start. Bunch of comments inline. Our mailer was nice enough to replace tabs
> with blanks, thanks to our friends at MicroSomething, so I could not run the patch
> through checkpatch.pl. Hope you did that.

Yes, I did.

>
> > ---
> > drivers/hwmon/Kconfig | 9 +
> > drivers/hwmon/Makefile | 1 +
> > drivers/hwmon/gpio-fan.c | 508 ++++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/gpio-fan.h | 43 ++++
> > 4 files changed, 561 insertions(+), 0 deletions(-)
> > create mode 100644 drivers/hwmon/gpio-fan.c
> > create mode 100644 include/linux/gpio-fan.h
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 4d4d09b..1dc57c1 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -399,6 +399,15 @@ config SENSORS_GL520SM
> > This driver can also be built as a module. If so, the module
> > will be called gl520sm.
> >
> > +config SENSORS_GPIO_FAN
> > + tristate "GPIO fan"
> > + depends on GENERIC_GPIO
> > + help
> > + If you say yes here you get support for the GPIO connected fan.
> > +
> > + This driver can also be built as a module. If so, the module
> > + will be called gpio-fan.
> > +
>
> Can you move this up a bit, ahead of SENSORS_FSCHMD ? Trying to stay in sequence.

Ok.

>
> > config SENSORS_CORETEMP
> > tristate "Intel Core/Core2/Atom temperature sensor"
> > depends on X86 && PCI && EXPERIMENTAL
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index e3c2484..a793e28 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -51,6 +51,7 @@ obj-$(CONFIG_SENSORS_FSCHMD) += fschmd.o
> > obj-$(CONFIG_SENSORS_G760A) += g760a.o
> > obj-$(CONFIG_SENSORS_GL518SM) += gl518sm.o
> > obj-$(CONFIG_SENSORS_GL520SM) += gl520sm.o
> > +obj-$(CONFIG_SENSORS_GPIO_FAN) += gpio-fan.o
> > obj-$(CONFIG_SENSORS_ULTRA45) += ultra45_env.o
> > obj-$(CONFIG_SENSORS_HDAPS) += hdaps.o
> > obj-$(CONFIG_SENSORS_I5K_AMB) += i5k_amb.o
> > diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c
> > new file mode 100644
> > index 0000000..6cc8205
> > --- /dev/null
> > +++ b/drivers/hwmon/gpio-fan.c
> > @@ -0,0 +1,508 @@
> > +/*
> > + * gpio-fan.c - Hwmon driver for GPIO connected fan.
> > + *
> > + * Copyright (C) 2010 LaCie
> > + *
> > + * Author: Simon Guinot <sguinot@lacie.com>
> > + *
> > + * 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.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write to the Free Software
> > + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/init.h>
> > +#include <linux/slab.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/irq.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/err.h>
> > +#include <linux/mutex.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/gpio.h>
> > +#include <linux/gpio-fan.h>
> > +
> > +struct gpio_fan_data {
> > + struct platform_device *pdev;
> > + struct device *hwmon_dev;
> > + struct mutex lock; /* lock GPIOs operations. */
> > + int num_ctrl;
> > + unsigned *ctrl;
> > + int ctrl_val;
> > + int num_speed;
> > + struct gpio_fan_speed *speed;
> > + int pwm_enable;
> > + struct gpio_fan_alarm *alarm;
> > + struct work_struct alarm_work;
> > + void (*platform_set_ctrl)(int num_ctrl, unsigned *ctrl, int ctrl_val);
> > +};
> > +
> > +/*
> > + * Alarm GPIO.
> > + */
> > +
> > +static void fan_alarm_notify(struct work_struct *ws)
> > +{
> > + struct gpio_fan_data *fan_data =
> > + container_of(ws, struct gpio_fan_data, alarm_work);
> > +
> > + sysfs_notify(&fan_data->pdev->dev.kobj, NULL, "fan1_alarm");
> > + kobject_uevent(&fan_data->pdev->dev.kobj, KOBJ_CHANGE);
> > +}
> > +
> > +static irqreturn_t fan_alarm_irq_handler(int irq, void *dev_id)
> > +{
> > + struct gpio_fan_data *fan_data = dev_id;
> > +
> > + schedule_work(&fan_data->alarm_work);
> > +
> > + return IRQ_HANDLED;
> > +}
> You are assuming that the irq does not have to be shared, and
> will always be handled. This may interfer with other drivers
> using the same IRQ for other GPIO pins.

Yes, you are right.

>
> > +
> > +static ssize_t show_fan_alarm(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct gpio_fan_data *fan_data = dev_get_drvdata(dev);
> > + struct gpio_fan_alarm *alarm = fan_data->alarm;
> > + int value = gpio_get_value(alarm->gpio);
> > +
> > + if (alarm->active_low)
> > + value = !value;
> > +
> > + return sprintf(buf, "%d\n", value);
> > +}
> > +
> > +static DEVICE_ATTR(fan1_alarm, S_IRUGO, show_fan_alarm, NULL);
> > +
> > +static int __devinit
> > +fan_alarm_init(struct gpio_fan_data *fan_data, struct gpio_fan_alarm *alarm)
> > +{
> > + int err;
> > + int alarm_irq;
> > + struct platform_device *pdev = fan_data->pdev;
> > +
> > + fan_data->alarm = alarm;
> > +
> > + err = gpio_request(alarm->gpio, "GPIO fan alarm");
> > + if (err)
> > + return err;
> > +
> > + err = gpio_direction_input(alarm->gpio);
> > + if (err)
> > + goto err_free_gpio;
> > +
> > + err = device_create_file(&pdev->dev, &dev_attr_fan1_alarm);
> > + if (err)
> > + goto err_free_gpio;
> > +
> > + INIT_WORK(&fan_data->alarm_work, fan_alarm_notify);
> > + alarm_irq = gpio_to_irq(alarm->gpio);
>
> gpio_to_irq() can return an error. Please check (I see that other drivers
> often don't check the return value, but that may be platform specific knowledge).

Yes, I have to check the returned value.

>
> Also, what happens if the gpio pin does not support interrupts in the first place ?
> Still need to be able to support alarms that case.

Good idea.

>
> > + set_irq_type(alarm_irq, IRQ_TYPE_EDGE_BOTH);
> > + err = request_irq(alarm_irq, fan_alarm_irq_handler, 0,
> > + "GPIO fan alarm", fan_data);
>
> Why not IRQF_SHARED ?

Simply because I have missed that.

>
> > + if (err)
> > + goto err_free_sysfs;
> > +
> > + return 0;
> > +
> > +err_free_sysfs:
> > + device_remove_file(&pdev->dev, &dev_attr_fan1_alarm);
> > +err_free_gpio:
> > + gpio_free(alarm->gpio);
> > +
> > + return err;
> > +}
> > +
> > +static void __devexit fan_alarm_free(struct gpio_fan_data *fan_data)
> > +{
> > + struct platform_device *pdev = fan_data->pdev;
> > +
> > + free_irq(gpio_to_irq(fan_data->alarm->gpio), fan_data);
>
> Please check for gpio_to_irq() error return.

Yes.

>
> > + device_remove_file(&pdev->dev, &dev_attr_fan1_alarm);
> > + gpio_free(fan_data->alarm->gpio);
> > +}
> > +
> > +/*
> > + * Control GPIOs.
> > + */
> > +
> > +static int __get_fan_ctrl(struct gpio_fan_data *fan_data)
> > +{
> > + int i;
> > + int ctrl_val = 0;
> > +
> > + for (i = 0; i < fan_data->num_ctrl; i++) {
> > + int value;
> > +
> > + value = gpio_get_value(fan_data->ctrl[i]);
> > + ctrl_val |= (value << i);
> > + }
> > + return ctrl_val;
> > +}
> > +
> > +static void __set_fan_ctrl(struct gpio_fan_data *fan_data, int ctrl_val)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < fan_data->num_ctrl; i++) {
> > + int value = !!(ctrl_val & (1 << i));
> > +
> value = (ctrl_val & (1 >> i));
> would be much simpler and easier to understand.
> Actually, you would not need 'value' in the first place.

I will simplify this function.

>
> > + gpio_set_value(fan_data->ctrl[i], value);
> > + }
> > +}
> > +
> > +static void set_fan_ctrl(struct gpio_fan_data *fan_data, int ctrl_val)
> > +{
> > + if (fan_data->platform_set_ctrl)
> > + fan_data->platform_set_ctrl(fan_data->num_ctrl, fan_data->ctrl,
> > + ctrl_val);
> > + else
> > + __set_fan_ctrl(fan_data, ctrl_val);
> > +
> > + fan_data->ctrl_val = ctrl_val;
> > +}
> > +
> > +static int rpm_to_ctrl(struct gpio_fan_data *fan_data, int rpm)
> > +{
> > + struct gpio_fan_speed *speed = fan_data->speed;
> > + int num_speed = fan_data->num_speed;
> > + int ctrl_val = speed[num_speed - 1].ctrl_val; /* Maximum speed */
> > + int i;
> > +
> > + for (i = 0; i < num_speed; i++) {
>
> { } not needed here.

Ok.

>
> > + if (speed[i].rpm >= rpm) {
> > + ctrl_val = speed[i].ctrl_val;
> > + break;
> > + }
> > + }
> > + return ctrl_val;
> > +}
> > +
> > +static int ctrl_to_rpm(struct gpio_fan_data *fan_data, int ctrl_val, int *rpm)
> > +{
>
> Since rpm is presumably always positive, you don't need a pointer to rpm.
> Return value can be rpm or error.

Yes.

>
> > + struct gpio_fan_speed *speed = fan_data->speed;
> > + int num_speed = fan_data->num_speed;
> > + int i;
> > +
> > + for (i = 0; i < num_speed; i++) {
>
> { } not needed here.

Yes.

>
> > + if (speed[i].ctrl_val == ctrl_val) {
> > + *rpm = speed[i].rpm;
> > + return 0;
> > + }
> > + }
> > + return -EINVAL;
> > +}
> > +
> > +static int pwm_to_rpm(struct gpio_fan_data *fan_data, u8 pwm)
> > +{
> > + int rpm_min = fan_data->speed[0].rpm;
> > + int rpm_max = fan_data->speed[fan_data->num_speed - 1].rpm;
> > +
> > + return rpm_min + DIV_ROUND_UP((rpm_max - rpm_min), 255) * pwm;
> > +}
> > +
> > +static u8 rpm_to_pwm(struct gpio_fan_data *fan_data, int rpm)
> > +{
> > + int rpm_min = fan_data->speed[0].rpm;
> > + int rpm_max = fan_data->speed[fan_data->num_speed - 1].rpm;
> > +
> > + return (rpm - rpm_min) / DIV_ROUND_UP((rpm_max - rpm_min), 255);
> > +}
> > +
> > +static ssize_t show_pwm(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct gpio_fan_data *fan_data = dev_get_drvdata(dev);
> > + int rpm;
> > + int ret;
> > +
> > + ret = ctrl_to_rpm(fan_data, fan_data->ctrl_val, &rpm);
> > + if (ret)
> > + return ret;
> > +
> > + return sprintf(buf, "%d\n", rpm_to_pwm(fan_data, rpm));
> > +}
> > +
> I don't really understand the value of supporting pwm attributes,
> since you have to convert those to rpm anyway. Why not just stick
> with fan1_input and fan1_target ? This would simplify the code a lot.

I don't know very well the hwmon API. I have simply been fooled by the
sysfs-interface document which claim that fan[1-*]_target only make
sense for a closed-loop fan. Moreover, I was expecting gpio-fan to be
compliant with the fancontrol shell script...

But anyway, you are right. I just don't want the pwm interface.

>
> fan1_min and fan1_max should be supported as well, especially
> since the information is provided anyway.

Yes.

>
> > +static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + struct gpio_fan_data *fan_data = dev_get_drvdata(dev);
> > + unsigned long pwm;
> > + int ctrl_val;
> > + int ret = count;
> > +
> > + if (strict_strtoul(buf, 10, &pwm) || pwm > 255)
> > + return -EINVAL;
> > +
> > + mutex_lock(&fan_data->lock);
> > +
> > + if (fan_data->pwm_enable != 1) {
> > + ret = -EPERM;
> > + goto exit_unlock;
> > + }
> > +
> > + ctrl_val = rpm_to_ctrl(fan_data, pwm_to_rpm(fan_data, (u8) pwm));
> > + if (ctrl_val != fan_data->ctrl_val)
> > + set_fan_ctrl(fan_data, ctrl_val);
> > +
> > +exit_unlock:
> > + mutex_unlock(&fan_data->lock);
> > +
> > + return ret;
> > +}
> > +
> > +static ssize_t show_pwm_enable(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct gpio_fan_data *fan_data = dev_get_drvdata(dev);
> > +
> > + return sprintf(buf, "%d\n", fan_data->pwm_enable);
> > +}
> > +
> > +static ssize_t set_pwm_enable(struct device *dev, struct device_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + struct gpio_fan_data *fan_data = dev_get_drvdata(dev);
> > + unsigned long val;
> > + int ctrl_val;
> > +
> > + if (strict_strtoul(buf, 10, &val) || val > 1)
> > + return -EINVAL;
> > +
> > + if (fan_data->pwm_enable == val)
> > + return count;
> > +
> > + mutex_lock(&fan_data->lock);
> > +
> > + fan_data->pwm_enable = val;
> > +
> > + /* Disable manual control mode: set fan at full speed. */
> > + if (val == 0) {
> > + ctrl_val = fan_data->speed[fan_data->num_speed - 1].ctrl_val;
> > + if (ctrl_val != fan_data->ctrl_val)
> > + set_fan_ctrl(fan_data, ctrl_val);
> > + }
> > +
> > + mutex_unlock(&fan_data->lock);
> > +
> > + return count;
> > +}
> > +
> > +static ssize_t show_pwm_mode(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + return sprintf(buf, "0\n");
> > +}
> > +
> > +static ssize_t show_rpm(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct gpio_fan_data *fan_data = dev_get_drvdata(dev);
> > + int ret;
> > + int rpm;
> > +
> > + ret = ctrl_to_rpm(fan_data, fan_data->ctrl_val, &rpm);
> > + if (ret < 0)
> > + return ret;
> > +
> > + return sprintf(buf, "%d\n", rpm);
> > +}
> > +
> > +static DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, show_pwm, set_pwm);
> > +static DEVICE_ATTR(pwm1_enable, S_IRUGO | S_IWUSR,
> > + show_pwm_enable, set_pwm_enable);
> > +static DEVICE_ATTR(pwm1_mode, S_IRUGO, show_pwm_mode, NULL);
> > +static DEVICE_ATTR(fan1_input, S_IRUGO, show_rpm, NULL);
> > +
> > +static struct attribute *gpio_fan_ctrl_attributes[] = {
> > + &dev_attr_pwm1.attr,
> > + &dev_attr_pwm1_enable.attr,
> > + &dev_attr_pwm1_mode.attr,
> > + &dev_attr_fan1_input.attr,
> > + NULL
> > +};
> > +
> > +static const struct attribute_group gpio_fan_ctrl_group = {
> > + .attrs = gpio_fan_ctrl_attributes,
> > +};
> > +
> > +static int __devinit fan_ctrl_init(struct gpio_fan_data *fan_data,
> > + struct gpio_fan_platform_data *pdata)
> > +{
> > + struct platform_device *pdev = fan_data->pdev;
> > + int num_ctrl = pdata->num_ctrl;
> > + unsigned *ctrl = pdata->ctrl;
> > + int i, err;
> > +
> > + for (i = 0; i < num_ctrl; i++) {
> > + err = gpio_request(ctrl[i], "GPIO fan control");
> > + if (err)
> > + goto err_free_gpio;
> > +
> > + err = gpio_direction_output(ctrl[i], gpio_get_value(ctrl[i]));
> > + if (err) {
> > + gpio_free(ctrl[i]);
> > + goto err_free_gpio;
> > + }
> > + }
> > +
> > + err = sysfs_create_group(&pdev->dev.kobj, &gpio_fan_ctrl_group);
> > + if (err)
> > + goto err_free_gpio;
> > +
> > + fan_data->num_ctrl = num_ctrl;
> > + fan_data->ctrl = ctrl;
> > + fan_data->platform_set_ctrl = pdata->set_ctrl;
> > + fan_data->num_speed = pdata->num_speed;
> > + fan_data->speed = pdata->speed;
> > + fan_data->pwm_enable = 1; /* Enable manual fan speed control. */
> > + if (pdata->get_ctrl)
> > + fan_data->ctrl_val = pdata->get_ctrl(num_ctrl, ctrl);
> > + else
> > + fan_data->ctrl_val = __get_fan_ctrl(fan_data);
> > +
> > + return 0;
> > +
> > +err_free_gpio:
> > + for (i = i - 1; i >= 0; i--)
> > + gpio_free(ctrl[i]);
> > +
> This misses the most recently allocated gpio pin if gpio_direction_output() failed.

The gpio is freed above while handling the gpio_direction_output() error.

>
> > + return err;
> > +}
> > +
> > +static void __devexit fan_ctrl_free(struct gpio_fan_data *fan_data)
> > +{
> > + struct platform_device *pdev = fan_data->pdev;
> > + int i;
> > +
> > + sysfs_remove_group(&pdev->dev.kobj, &gpio_fan_ctrl_group);
> > + for (i = 0; i < fan_data->num_ctrl; i++)
> > + gpio_free(fan_data->ctrl[i]);
> > +}
> > +
> > +/*
> > + * Platform driver.
> > + */
> > +
> > +static ssize_t show_name(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + return sprintf(buf, "gpio-fan\n");
> > +}
> > +
> > +static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
> > +
> > +static int __devinit gpio_fan_probe(struct platform_device *pdev)
> > +{
> > + int err = 0;
> > + struct gpio_fan_data *fan_data;
> > + struct gpio_fan_platform_data *pdata = pdev->dev.platform_data;
> > +
> > + if (!pdata)
> > + return -EINVAL;
> > +
> > + fan_data = kzalloc(sizeof(struct gpio_fan_data), GFP_KERNEL);
> > + if (!fan_data)
> > + return -ENOMEM;
> > +
> > + fan_data->pdev = pdev;
> > + platform_set_drvdata(pdev, fan_data);
> > + mutex_init(&fan_data->lock);
> > +
> > + /* Configure alarm GPIO if available. */
> > + if (pdata->alarm) {
> > + err = fan_alarm_init(fan_data, pdata->alarm);
> > + if (err)
> > + goto err_free_data;
> > + }
> > +
> > + /* Configure control GPIOs if available. */
> > + if (pdata->ctrl && pdata->num_ctrl) {
> > + if (!pdata->num_speed || !pdata->speed) {
> > + err = -EINVAL;
> > + goto err_free_alarm;
> > + }
> > + err = fan_ctrl_init(fan_data, pdata);
> > + if (err)
> > + goto err_free_alarm;
> > + }
> > +
> > + err = device_create_file(&pdev->dev, &dev_attr_name);
> > + if (err)
> > + goto err_free_ctrl;
> > +
> > + /* Make this driver part of hwmon class. */
> > + fan_data->hwmon_dev = hwmon_device_register(&pdev->dev);
> > + if (IS_ERR(fan_data->hwmon_dev)) {
> > + err = PTR_ERR(fan_data->hwmon_dev);
> > + goto err_remove_name;
> > + }
> > +
> > + dev_info(&pdev->dev, "GPIO fan initialized\n");
> > +
> Might be a good idea to add a notion of which fan was initialized.
> After all, there could be more than one.

dev_info() don't do it for me ? anyway, I will check this too.

>
> > + return 0;
> > +
> > +err_remove_name:
> > + device_remove_file(&pdev->dev, &dev_attr_name);
> > +err_free_ctrl:
> > + fan_ctrl_free(fan_data);
>
> Might want to check for fan_data->ctrl to be consistent with the code below.

Of course...

>
> > +err_free_alarm:
> > + fan_alarm_free(fan_data);
>
> This will crash if fan_data->alarm is NULL.

...

>
> > +err_free_data:
> > + platform_set_drvdata(pdev, NULL);
> > + kfree(fan_data);
> > +
> > + return err;
> > +}
> > +
> > +static int __devexit gpio_fan_remove(struct platform_device *pdev)
> > +{
> > + struct gpio_fan_data *fan_data = platform_get_drvdata(pdev);
> > +
> > + hwmon_device_unregister(fan_data->hwmon_dev);
> > + device_remove_file(&pdev->dev, &dev_attr_name);
> > + if (fan_data->alarm)
> > + fan_alarm_free(fan_data);
> > + if (fan_data->ctrl)
> > + fan_ctrl_free(fan_data);
> > + kfree(fan_data);
> > +
> > + return 0;
> > +}
> > +
> > +static struct platform_driver gpio_fan_driver = {
> > + .probe = gpio_fan_probe,
> > + .remove = __devexit_p(gpio_fan_remove),
> > + .driver = {
> > + .name = "gpio-fan",
> > + },
> > +};
> > +
> > +static int __init gpio_fan_init(void)
> > +{
> > + return platform_driver_register(&gpio_fan_driver);
> > +}
> > +
> > +static void __exit gpio_fan_exit(void)
> > +{
> > + platform_driver_unregister(&gpio_fan_driver);
> > + return;
> > +}
> > +
> > +module_init(gpio_fan_init);
> > +module_exit(gpio_fan_exit);
> > +
> > +MODULE_AUTHOR("Simon Guinot <sguinot@lacie.com>");
> > +MODULE_DESCRIPTION("GPIO FAN driver");
> > +MODULE_LICENSE("GPL");
> > +MODULE_ALIAS("platform:gpio-fan");
> > diff --git a/include/linux/gpio-fan.h b/include/linux/gpio-fan.h
> > new file mode 100644
> > index 0000000..58f0930
> > --- /dev/null
> > +++ b/include/linux/gpio-fan.h
> > @@ -0,0 +1,43 @@
> > +/*
> > + * include/linux/gpio-fan.h
> > + *
> > + * Platform data structure for GPIO fan driver
> > + *
> > + * This file is licensed under the terms of the GNU General Public
> > + * License version 2. This program is licensed "as is" without any
> > + * warranty of any kind, whether express or implied.
> > + */
> > +
> > +#ifndef __LINUX_GPIO_FAN_H
> > +#define __LINUX_GPIO_FAN_H
> > +
> > +struct gpio_fan_alarm {
> > + unsigned gpio;
> > + unsigned active_low;
> > +};
> > +
> > +struct gpio_fan_speed {
> > + int rpm;
> > + int ctrl_val;
> > +};
> > +
> > +struct gpio_fan_platform_data {
> > + int num_ctrl;
> > + unsigned *ctrl; /* fan control GPIOs. */
> > + struct gpio_fan_alarm *alarm; /* fan alarm GPIO. */
> > + /*
> > + * Speed conversion array: rpm from/to GPIO bit field.
> > + * This array _must_ be sorted in ascending rpm order.
> > + */
> > + int num_speed;
> > + struct gpio_fan_speed *speed;
> > + /*
> > + * This functions can be supplied if some specific operations are
> > + * required to get/set a fan control (handle a latch enable GPIO,
> > + * prevent from writing some transitional control value, etc...)
> > + */
> > + int (*get_ctrl)(int num_ctrl, unsigned *ctrl);
> > + void (*set_ctrl)(int num_ctrl, unsigned *ctrl, int ctrl_val);
>
> Not sure if this is a good/useful API. It expects that the called function
> identifies the fan from the ctrl[] array. Not sure how clumsy the resulting code
> might be. It may be better to leave the API out for now until someone actually
> writes a driver (hint, hint, dns323) using it.

I agree and I will happily throw away the clumsy API :)

Simon
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