From mboxrd@z Thu Jan  1 00:00:00 1970
From: mindentropy@gmail.com (mind entropy)
Date: Sun, 10 Aug 2014 13:27:37 +0530
Subject: On platform device template.
Message-ID: <CAM2a4uwBxGgOPWp1P0zAXdv-QX6A=Smy4xDBLYb_hqsgJsXkyw@mail.gmail.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Hi,

  I am testing out the platform driver and would like to know the
template for platform device register/unregister.

  The following code causes a crash whenever the device gets unregistered.

---------------------------------------------------
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/device.h>

struct test_platform_data {
    int x;
    int y;
};

static struct test_platform_data test_pd = {
    .x = 2,
    .y = 3,
};

static struct platform_device test_platform_device = {
    .name = "test-plat",
    .id = -1,
    .resource = NULL,
    .num_resources = 0,
    .dev = {
        .platform_data = &test_pd,
    }
};

static int __init platform_driver_test_init(void) {
    int retval = 0;

    printk(KERN_ALERT "Platform driver init\n");

    retval = platform_device_register(&test_platform_device);

    if(retval != 0) {
        printk(KERN_ALERT "Could not register platform device\n");
        return retval;
    } else {
        printk(KERN_ALERT "Registered platform device\n");
        printk(KERN_ALERT "Unregistering\n");

        platform_device_unregister(&test_platform_device);

    }

    return 0;
}

static void __exit platform_driver_test_exit(void) {
    printk(KERN_ALERT "Platform driver exit\n");
}

module_init(platform_driver_test_init);
module_exit(platform_driver_test_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("TEST");
MODULE_DESCRIPTION("Platform driver test");

---------------------------------------------------

Should the platform device be created using platform_device_alloc(..)
and added using platform_device_add(..)  like the below code?


----------------------------------------------------
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/device.h>

struct test_platform_data {
    int x;
    int y;
};

static struct test_platform_data test_pd = {
    .x = 2,
    .y = 3,
};


static struct platform_device *test_platform_device;

static int __init platform_driver_test_init(void) {
    int retval = 0;

    printk(KERN_ALERT "Platform driver init\n");

    test_platform_device = platform_device_alloc("test-plat",-1);

    if(test_platform_device == NULL) {
        printk(KERN_ALERT "Could not allocate platform device\n");

        return 0;
    }

    platform_device_add_data(test_platform_device,&test_pd,sizeof(test_pd));

    retval = platform_device_add(test_platform_device);

    if(retval != 0) {
        printk(KERN_ALERT "Could not register platform device\n");
        return retval;
    } else {
        printk(KERN_ALERT "Registered platform device\n");
        printk(KERN_ALERT "Unregistering\n");

        platform_device_unregister(test_platform_device);

    }


    return 0;
}

static void __exit platform_driver_test_exit(void) {
    printk(KERN_ALERT "Platform driver exit\n");
}

module_init(platform_driver_test_init);
module_exit(platform_driver_test_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("TEST");
MODULE_DESCRIPTION("Platform driver test");

----------------------------------------------------


Thanks,
Gautam.