Programming


/*
 * Character driver for ARM STM32 chip GPIO port implemented
 * separately for inputs and outputs
 *
 * Copyright © 2013 Lukasz Kazmierczak
 */

#include ...

#define DRIVER_NAME         "io-gpio"
#define PFX DRIVER_NAME     ": "

#define DRIVER_DEVICES_NB   2U
#define MAX_GPIO_RANGE      16U

static int initialize_gpio_inputs(void);
static int initialize_gpio_outputs(void);


struct gpio_data {
    atomic_t open_count;
};

struct group_data {
    dev_t dev_node;
    struct cdev cdev;
    struct resource *gpio_range;
    struct gpio_data *gpios;
};

typedef struct group_data group_data_struct;

group_data_struct *group_data_vect[DRIVER_DEVICES_NB] = {0};


int initialize_gpio_inputs()
{
    int i=0, ret=-1;

    for(i=0; i < MAX_GPIO_RANGE; i++)
        gpio_direction_input(i, 1);

    if(i == MAX_GPIO_RANGE)
        ret = 0;

    return ret;
}

int initialize_gpio_outputs()
{
    int i=0, ret = -1;

    for(i=0; i < MAX_GPIO_RANGE; i++)
    {
        gpio_direction_output(i, 0);
        gpio_set_value(i, 0);
    }

    if(i == MAX_GPIO_RANGE)
        ret = 0;

    return ret;
}

/**
 *  simple_gpio_read - readout pin status from input port 
 *  ex. $ cat /dev/gpioG8
 */
static ssize_t simple_gpioin_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
{
    unsigned int gpio = iminor(file->f_path.dentry->d_inode);
    static char *buf_signature = 0;
    ssize_t ret = 0;

    //printk("gpio read requested from input port: count %d, buf %p\n", count, buf);

    if(count > 1 && buf_signature == buf)
    {
        //second call for exceeding data readout, abort reading
        buf_signature = 0;
        count = 0;
    }
    else if(count > 1) {
        //first call for exceeding data readout, return available reading
        buf_signature = buf;
        count = 3;
    }
    else {
        //no action defined
    }

    char byte = '0';
    gpio_direction_input(gpio, 1);
    byte += gpio_get_value(gpio);
    //printk("Input readout for pin: %d is %c\n", gpio, byte);
    ret = count;
    if(count > 2) {
        if (put_user(byte, buf) || put_user('\n', buf + 1) || put_user('\0', buf + 2))
            ret = -1;
    }
    else if(count == 1){
        if (put_user(byte, buf))
            ret = -1;
    }
    else {
        //no action defined
    }

    return ret;
}

/**
 *  simple_gpio_read - readout pin status from output port: no action 
 *  ex. $ cat /dev/gpioF8
 */
static ssize_t simple_gpio_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
{
    ssize_t ret = -1;

    printk("gpio read requested for output port: operation not supported\n");
    return ret;
}

/**
 *  simple_gpioin_write - set pin state of input port to desired value: no action
 *  ex. $ echo '1' > /dev/gpioG8
 */
static ssize_t
simple_gpioin_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
    ssize_t ret = -1;

    printk("write requested for input port: operation not supported!\n");
    return ret;
}

/**
 *  simple_gpio_write - set pin state of output port to desired value
 *  ex. $ echo '1' > /dev/gpioF8
 */
static ssize_t
simple_gpio_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
    unsigned int gpio = iminor(file->f_path.dentry->d_inode);
    ssize_t i = 0, ret = -1;
    char uvalue = 0;
    int value = 0;
    //printk("gpio write requested for output port: count %d, buf %p\n", count, buf);

    i = 0;
    while (i < count)
    {
        char byte = 0;
        int user_ret = get_user(byte, buf + i);

        i++;
        if (user_ret)
            return user_ret;

        switch (byte) {
            case '\r':
            case '\n':
                  continue;
            case 'T':
            case '0':
            case '1': uvalue = byte;
                  break;
            default:
                uvalue = 0;
                i = count;
        }
        GPIO_DBG("processed byte '%c'", byte);
    }

    if(uvalue != 0) {
        switch (uvalue) {
            case 'T': value = !gpio_get_output_value(gpio);
                  break;
            default:  value = uvalue - '0';
        }

        gpio_direction_output(gpio, 0);
        gpio_set_value(gpio, value);

        ret = count;
    }

    return ret;
}

/**
 *  simple_gpio_open - allocate specific pin of GPIO port to be accessed
 *
 */
static int simple_gpio_open(struct inode *ino, struct file *file)
{
    struct group_data *group_data = container_of(ino->i_cdev, struct group_data, cdev);
    unsigned int gpio = iminor(ino);
    struct gpio_data *gpio_data = &group_data->gpios[gpio - group_data->gpio_range->start];
    int ret;

    if (gpio < group_data->gpio_range->start || gpio > group_data->gpio_range->end)
        return -ENXIO;

    ret = gpio_request(gpio, DRIVER_NAME);
    if (ret)
        return ret;

    atomic_inc(&gpio_data->open_count);

    return 0;
}

/**
 *  simple_gpio_close - deallocate specific pin of GPIO port from being accessed
 *
 */
static int simple_gpio_release(struct inode *ino, struct file *file)
{
    struct group_data *group_data = container_of(ino->i_cdev, struct group_data, cdev);
    unsigned int gpio = iminor(ino);
    struct gpio_data *gpio_data = &group_data->gpios[gpio - group_data->gpio_range->start];

    /* do not free until last consumer has closed */
    if (atomic_dec_and_test(&gpio_data->open_count))
        gpio_free(gpio);
    else
        GPIO_DBG("gpio still in use -- not freeing");

    return 0;
}

static int simple_gpio_ioctl(struct inode * ino, struct file * file, unsigned int a, unsigned long b)
{
    return 0;
}

static struct class *simple_gpio_class;

/**
 *  simple_gpio_fops - define operations for specific resource
 *
 */
static struct file_operations simple_gpio_fops[] = {
    [0] =   {
        .owner    = THIS_MODULE,
        .read     = simple_gpio_read,
        .write    = simple_gpio_write,
        .open     = simple_gpio_open,
        .release  = simple_gpio_release,
        .ioctl    = simple_gpio_ioctl,
    },
    [1] =   {
        .owner    = THIS_MODULE,
        .read     = simple_gpioin_read,
        .write    = simple_gpioin_write,
        .open     = simple_gpio_open,
        .release  = simple_gpio_release,
        .ioctl    = simple_gpio_ioctl,
    },
};

/**
 *  simple_gpio_probe - allocate resources and bind as character devices
 *
 */
static int __devinit simple_gpio_probe(struct platform_device *pdev)
{
    int ret = 0, dev = 0;
    char *devName[][DRIVER_DEVICES_NB] = {
                            { "gpio", "gpio%i"     },
                            { "gpioin", "gpioin%i" },
                             };
    group_data_struct *(*group_data_init)[DRIVER_DEVICES_NB] = kzalloc(sizeof(group_data_vect), GFP_KERNEL);

    platform_set_drvdata(pdev, group_data_init);
    while(dev < DRIVER_DEVICES_NB)
    {
        struct group_data *group_data;
        struct resource *gpio_range = platform_get_resource(pdev, IORESOURCE_IRQ, dev);
        int gpio, gpio_max = gpio_range->end - gpio_range->start + 1;

        group_data = kzalloc(sizeof(*group_data) + sizeof(struct gpio_data) * gpio_max, GFP_KERNEL);

        if (!group_data)
            return -ENOMEM;

        group_data->gpio_range = gpio_range;
        group_data->gpios = (void *)group_data + sizeof(*group_data);
        (*group_data_init)[dev] = group_data;

        ret = alloc_chrdev_region(&group_data->dev_node, gpio_range->start, gpio_max, devName[dev][0]);

        if (ret) {
            pr_devinit(KERN_ERR PFX "unable to get a char device\n");
            kfree(group_data);
            return ret;
        }

        cdev_init(&group_data->cdev, &simple_gpio_fops[dev]);
        group_data->cdev.owner = THIS_MODULE;

        ret = cdev_add(&group_data->cdev, group_data->dev_node, gpio_max);
        if (ret) {
            pr_devinit(KERN_ERR PFX "unable to register char device\n");
            unregister_chrdev_region(group_data->dev_node, gpio_max);
            kfree(group_data);
            return ret;
        }

        for (gpio = gpio_range->start; gpio <= gpio_range->end; ++gpio)
        {
            device_create(simple_gpio_class, &pdev->dev, group_data->dev_node + gpio,
                          NULL, devName[dev][1], (int)gpio);
        }

        device_init_wakeup(&pdev->dev, 1);

        pr_devinit(KERN_INFO PFX "Dev %d: now handling %i GPIOs: %i - %i, registered as %d\n",
                dev+1, gpio_max, gpio_range->start, gpio_range->end, MAJOR(group_data->dev_node) );

        dev++;
    }

    if(ret == 0) {
        //no error occured, no further action needed
    }
    else if(dev > 0) {
        //ToDo
        //initisalization of second resource failed
        //uninitialization has to be done for the first resource
    }
    else {
        //ToDo
        //first resorce initialization failed and is uninitialized
        //second resource is not to be initialized
    }

    return ret;
}

/**
 *  simple_gpio_remove - remove character devices of GPIO resources.
 */
static int __devexit simple_gpio_remove(struct platform_device *pdev)
{
    int ret = 0, dev = 0;
    group_data_struct *(*group_data_deinit)[DRIVER_DEVICES_NB]=platform_get_drvdata(pdev);

    while(dev < DRIVER_DEVICES_NB)
    {
        struct group_data *group_data = (*group_data_deinit)[dev];
        struct resource *gpio_range = group_data->gpio_range;
        int gpio=0, gpio_max=gpio_range->end - gpio_range->start + 1;

        for (gpio = gpio_range->start; gpio <= gpio_range->end; ++gpio)
            device_destroy(simple_gpio_class, group_data->dev_node + gpio);

        cdev_del(&group_data->cdev);
        unregister_chrdev_region(group_data->dev_node, gpio_max);

        kfree(group_data);
        dev++;
    }
    kfree(group_data_deinit);

    return ret;
}

struct platform_driver simple_gpio_device_driver = {
    .probe   = simple_gpio_probe,
    .remove  = __devexit_p(simple_gpio_remove),
    .driver  = {
        .name = DRIVER_NAME,
    }
};

/**
 *  simple_gpio_init - initial startup of GPIO driver
 *
 */
static int __init simple_gpio_init(void)
{
    //initialize_gpio_inputs();
    //initialize_gpio_outputs();

    simple_gpio_class = class_create(THIS_MODULE, DRIVER_NAME);
    if (IS_ERR(simple_gpio_class)) {
        pr_init(KERN_ERR PFX "unable to create gpio class\n");
        return PTR_ERR(simple_gpio_class);
    }

    return platform_driver_register(&simple_gpio_device_driver);
}

module_init(simple_gpio_init);

/**
 *  simple_gpio_exit - dropping GPIO device driver
 */
static void __exit simple_gpio_exit(void)
{
    class_destroy(simple_gpio_class);

    platform_driver_unregister(&simple_gpio_device_driver);
}
module_exit(simple_gpio_exit);

MODULE_AUTHOR("Lukasz Kazmierczak");
MODULE_DESCRIPTION("STM32 input/output port driver");
MODULE_LICENSE("GPL");