On 8/14/08, Bartek Dolewski <[EMAIL PROTECTED]> wrote:
> Hi all
> I`ve written my first character device which can read and write. I think
> that read and write functions are ok but it seems to be some errors during
> initialization my device. Here is the source code:
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/init.h>
> #include <linux/fs.h>
> #include <linux/cdev.h>
> #include <asm/uaccess.h>
>
> static int FirstModuleInit(void);
> static void FirstModuleExit(void);
>
> static int FirstModule_Open(struct inode *, struct file *);
> static int FirstModule_Release(struct inode *, struct file *);
> static ssize_t FirstModule_Read(struct file *, char *, size_t, loff_t *);
> static ssize_t FirstModule_Write(struct file *, const char *, size_t,
> loff_t *);
>
> #define DEV_LICENSE "GPL"
> #define SUCCESS 0
> #define DEVICE_NAME "mydevice"
> #define BUF_LEN 128
>
> static int Major;
> static int Device_Open = 0;
>
> static char msg[BUF_LEN];
> static char *msg_Ptr;
>
> static struct cdev* my_cdev;
Should be not poiter but normal structure:
static struct cdev my_cdev;
>
> static struct file_operations fops = {
> .read = FirstModule_Read,
> .write = FirstModule_Write,
> .open = FirstModule_Open,
> .release = FirstModule_Release
> };
>
> static int FirstModuleInit(void)
> {
> int result, err;
> dev_t dev = 0;
>
> result = alloc_chrdev_region(&dev, 0, 1, DEVICE_NAME);
> Major = MAJOR(dev);
>
> if (result < 0 ) {
> printk(KERN_WARNING "First: unable to get major number-> %d",Major);
> return result;
> }
>
Than here small modifications:
> cdev_init(my_cdev, &fops);
cdev_init(&my_cdev, &fops);
> my_cdev->owner = THIS_MODULE;
my_cdev.owner = THIS_MODULE;
> my_cdev->ops = &fops;
my_cdev.ops = &fops;
> err = cdev_add(my_cdev, dev, 1);
err = cdev_add(&my_cdev, dev, 1);
>
> if (err)
> printk(KERN_NOTICE "Error during adding %s device", DEVICE_NAME);
>
> printk(KERN_INFO "I was assigned major number %d. To talk to\n", Major);
> printk(KERN_INFO "My dev = %d", dev);
> printk(KERN_INFO "'mknod /dev/%s c %d 0'\n", DEVICE_NAME, Major);
>
> return SUCCESS;
> }
>
> static void FirstModuleExit(void)
> {
> cdev_del(my_cdev);
cdev_del(&my_cdev);
> }
>
> static int FirstModule_Open(struct inode *inode, struct file *file)
> {
> static int counter = 0;
> if(Device_Open)
> return -EBUSY;
>
> Device_Open++;
> sprintf(msg, "I`ve already told you %d times Hello World!\n",
> counter++);
> msg_Ptr = msg;
> try_module_get(THIS_MODULE);
>
> return SUCCESS;
> }
>
> static int FirstModule_Release(struct inode *inode, struct file *file)
> {
> Device_Open--;
> module_put(THIS_MODULE);
> return 0;
> }
>
> static ssize_t FirstModule_Read(struct file *flip, char *buffer, size_t
> length, loff_t *offset)
> {
> int bytes_read = 0;
> if(*msg_Ptr == 0)
> return 0;
>
> while(length && *msg_Ptr){
> put_user( *(msg_Ptr++), buffer++);
> length--;
> bytes_read++;
> }
> return bytes_read;
> }
>
> static ssize_t FirstModule_Write(struct file *flip, const char *buffer,
> size_t length, loff_t *off)
> {
> int i;
> for(i=0; i < length && i < BUF_LEN; i++)
> get_user(msg[i],buffer+i);
> msg_Ptr = msg;
> printk(KERN_INFO "Your message from Userland is: %s",msg);
> return i;
> }
>
> /*licence of the module*/
> module_init(FirstModuleInit);
> module_exit(FirstModuleExit);
>
> MODULE_LICENSE(DEV_LICENSE);
> MODULE_AUTHOR("Bartosz Dolewski");
> MODULE_DESCRIPTION("Simple char device ");
> MODULE_SUPPORTED_DEVICE("TestDevice");
>
> I guess that I made something wrong with major and minor numbers or with
> dev_t dev. I just wanted to dynamically register this device not at compile
> time. Here is dmesg output message:
>
> RIP: 0010:[<ffffffff803142e0>] [<ffffffff803142e0>] memset_c+0x20/0x30
> RSP: 0018:ffff81002cca7e20 EFLAGS: 00010212
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000000d
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff81002fecc6c0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000200200 R11: 0000000000000001 R12: ffffffff88384ba0
> R13: 0000000000000011 R14: ffffc200004f3b98 R15: 0000000000000001
> FS: 00002b2c2017a6e0(0000) GS:ffff8100375f8ac0(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 0000000000000000 CR3: 0000000036098000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process insmod (pid: 3325, threadinfo ffff81002cca6000, task
> ffff8100376a9800)
> Stack: ffffffff8029a6cf 0000000000000001 0000000000000000 ffffffff88384c80
> ffffffff88384102 0000000000000011 0fa00000004f3b98 ffffffff88384c80
> ffffffff80256c30 0000000000002ac7 0000000000000000 0000000000000000
> Call Trace:
> [<ffffffff8029a6cf>] cdev_init+0x19/0x3e
> [<ffffffff88384102>] :first:FirstModuleInit+0x61/0xe4
> [<ffffffff80256c30>] sys_init_module+0x16e3/0x1821
> [<ffffffff8020be2e>] system_call+0x7e/0x83
>
>
> Code: f3 48 ab 44 89 c1 f3 aa 4c 89 c8 c3 0f 1f 40 00 eb ce 66 66
> RIP [<ffffffff803142e0>] memset_c+0x20/0x30
> RSP <ffff81002cca7e20>
> CR2: 0000000000000000
> ---[ end trace adc72f43f989e1df ]---
> Of course insmod failed with "Terminated" message. I was learning from
> http://tldp.org/LDP/lkmpg/2.6/html/x569.html but as far as
> I know there are old way (register_chrdev()). I would like to use new
> structure cdev but I can see it is to sophisticated for me.
> Thanks for any help
> --
> -----BEGIN GEEK CODE BLOCK-----
> GCS d- s:- a--- C+++ P L+++>+++++ E---- W+ N+ o? K- w--- O- M- V? PS++ PE++
> Y PGP++ t--- 5? X R tv-- b+ DI+ D- G++ e- h! !r(--) !z+
> ------END GEEK CODE BLOCK------
>
Than it works for 100% (I test it). Enjoy
Marek
--
Marek Beliško
Ruská Nová Ves 219
08005 Prešov
Slovakia
http://binaural.ifastnet.com
