I am developing this module for custom device that, in fact, a 4*8-bit i-o ports attached to ISA bus with addresses 0x0120 - 0x0123. This driver is based on "scull" by Alessandro Rubini and Jonathan Corbet. My OS is Ubuntu 10.04, kernel is 2.6.32-74 generic, I use built-in console-oriented compiler gcc. While inserting compiled module using "insmod" I get an error "bad address" and module was not loaded. I've tried to debug it using "printk" and found out that my module successfully gets a range of i-o ports, major and minor numbers and then, when trying to do "Reset_Port" function it generates an error "bad address" and exits.
Can anybody tell me, what am I doing wrong?
Here are __exit and __init functions of my module
void __exit ET3201_exit(void)
{
int i;
dev_t devno = MKDEV(ET3201_major, ET3201_minor);
/* Get rid of our char dev entries */
if (ET3201_devices) {
for (i = 0; i < ET3201_nr_devs; i++) {
ET3201_trim(ET3201_devices + i);
cdev_del(&ET3201_devices[i].cdev);
}
kfree(ET3201_devices);
}
#ifdef ET3201_DEBUG /* use proc only if debugging */
ET3201_remove_proc();
#endif
/* cleanup_module is never called if registering failed */
unregister_chrdev_region(devno, ET3201_nr_devs);
if ( ! port ) release_region(BaseIO, 8);
printk(KERN_INFO "Goodbye, cruel world - ET3201 is unloaded\n");
/* and call the cleanup functions for friend devices */
/*ET3201_access_cleanup();*/
}
/*----------------------------------------------------------------------------*/
/* Set up the char_dev structure for this device. */
static void ET3201_setup_cdev(struct ET3201_dev *dev, int index)
{
int err, devno = MKDEV(ET3201_major, ET3201_minor + index);
cdev_init(&dev->cdev, &ET3201_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &ET3201_fops;
dev->CAMAC_Module_Number = CAMAC_Nmod;
dev->CAMAC_Command_Adress = CAMAC_Adcom;
dev->Driver_Number = ET3201_minor + index;
err = cdev_add (&dev->cdev, devno, 1);
/* Fail gracefully if need be */
if (err)
printk(KERN_NOTICE "Error %d adding ET3201%d", err, index);
}
/*----------------------------------------------------------------------------*/
int __init ET3201_init(void)
{
int result = 0;
int i;
dev_t dev = 0;
BaseIO = Base;
/* Get a range of minor numbers to work with, asking for a dynamic
major unless directed otherwise at load time. */
if (ET3201_major) {
dev = MKDEV(ET3201_major, ET3201_minor);
result = register_chrdev_region(dev, ET3201_nr_devs, "ET3201");
} else {
result = alloc_chrdev_region(&dev, ET3201_minor, ET3201_nr_devs, "ET3201");
ET3201_major = MAJOR(dev);
}
if (result < 0) {
printk(KERN_WARNING "ET3201: can't get major %d\n", ET3201_major);
return result;
}
port = request_region(BaseIO, 8, "ET3201");
if ( port == NULL ) {
printk(KERN_WARNING "ET3201 cannot reserve i-o ports %lu \n", BaseIO);
return -ENODEV;
goto fail;
}
/*
* allocate the devices -- we can't have them static, as the number
* can be specified at load time
*/
ET3201_devices = kmalloc(ET3201_nr_devs * sizeof(struct ET3201_dev), GFP_KERNEL);
if (! ET3201_devices) {
result = -ENOMEM;
printk(KERN_ALERT "ET3201: can't get memory \n");
goto fail; /* Fail gracefully if need be */
}
memset(ET3201_devices, 0, ET3201_nr_devs * sizeof(struct ET3201_dev));
/* Initialize each device. */
for (i = 0; i < ET3201_nr_devs; i++) {
ET3201_devices[i].quantum = ET3201_quantum;
ET3201_devices[i].qset = ET3201_qset;
init_MUTEX(&ET3201_devices[i].sem);
ET3201_setup_cdev(&ET3201_devices[i], i);
}
/* At this point call the init function for any friend device */
dev = MKDEV(ET3201_major, ET3201_minor + ET3201_nr_devs);
/*dev += ET3201_access_init(dev);*/
printk(KERN_INFO "ET3201 is initialized with major %d\n", ET3201_major);
if ( port != NULL ){
printk(KERN_INFO "ET3201 is trying to reset %d devices\n", ET3201_nr_devs);
result = Reset_Port();
}
if ( result != 0 ) {
printk(KERN_ALERT "ET3201: device cannot reset with result %d\n", result);
result = -EFAULT;
goto fail;
}
#ifdef ET3201_DEBUG /* only when debugging */
ET3201_create_proc();
#endif
return 0; /* succeed */
fail:
ET3201_exit();
return result;
}
/*----------------------------------------------------------------------------*/
module_init(ET3201_init);
module_exit(ET3201_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(ET3201_minor);
and next will be Reset_Port()
static int Reset_Port(void)
{
int result = -EIO;
int count;
if (port == NULL) goto fail;
for ( count = 0; count < ET3201_nr_devs; count++ )
{
outb(0x00, ports[count]);
}
wmb(); /*write memory barrier*/
LastOp = E_Reset;
result = 0; /* success */
fail:
return result;
}
EXPORT_SYMBOL(Reset_Port);
Now, after fixing 'int Reset_Port(void)' I've got another problem -
'WARNING: modpost: Found 1 section mismatch(es).'
After debugging I see that this is a result of calling 'ET3201_exit()'
from 'module_init()' - when I remarked this call, warning disappeared.
Surprising that exactly the same call was made in "scull" driver of respected authors - and it works.
Question: What can lead to kernel mismatch in this code?
Yes! The bug is fixed - after declaring ' int Reset_Port(void) ' the module was inserted and removed successfully. I thought,(but it was wrong) that all functions that can be called from within ' module_init() ' must not be declared as static.