On Tue, Dec 9, 2008 at 11:34 AM, Chetan Nanda <chetannanda@xxxxxxxxx> wrote:
This issue is resolved, problem is indeed in my driver cleanup function.
unregister_chrdev_region(
But still i an not able to figure out that how chrdevs[i] (in fs/char_dev.c) is getting NULL in unregister_chrdev_region
On Mon, Dec 8, 2008 at 9:35 PM, Sandeep K Sinha <sandeepksinha@xxxxxxxxx> wrote:
On Mon, Dec 8, 2008 at 7:45 PM, Chetan Nanda <chetannanda@xxxxxxxxx> wrote:/* temporary */
> Hi,
>
> I am using 'alloc_chrdev_region' for registering char device range and then
> 'unregister_chrdev_region' for un-registering it.
> But on each insmod I am getting MAJOR number as one less then that of
> previous time.
96 if (major == 0) {
97 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
98 if (chrdevs[i] == NULL)
99 break;
100 }
101
102 if (i == 0) {
103 ret = -EBUSY;
104 goto out;
105 }
106 major = i;
107 ret = major;
108 }
109
REF: http://lxr.oss.org.cn/source/fs/char_dev.c#L80
>Thats right, it is like that.
> On seeing the code (unregister_chrdev_region) it seems that it just kfree
> the chrdevs[] entry but not set it to NULL which cause for new
> entry in chrdevs[].
>
Dont have much idea regarding the same. I think we should assign a
NULL to it for sure.I have tried with setting chrdevs entry to NULL after kfree but it didn't help
void unregister_chrdev_region(dev_t from, unsigned count)
{
dev_t to = from + count;
dev_t n, next;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
if (next > to)
next = to;
kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
}
/*I do it*/
chrdevs[MAJOR(n)] = NULL; //<--- setting it to null here
}
It seems that problem is in my test driver implementation.
Here are my init and clean-up function:
int __init
cmos_init(void)
{
int i;
/*Clear cmosdev_array struct*/
memset((void *)&cmosdev_array, 0 , sizeof(struct cmos_dev*) * NUM_CMOS_BANKS);
/* Request dynamic allocation of a device major number */
if (alloc_chrdev_region(&cmos_dev_number, 0, NUM_CMOS_BANKS, DEVICE_NAME) < 0)
{
printk(KERN_DEBUG "Can't register device\n"); return -1;
}
/* Populate sysfs entries */
cmos_class = class_create(THIS_MODULE, DEVICE_NAME);
for (i=0; i<NUM_CMOS_BANKS; i++)
{
/* Allocate memory for the per-device structure */
cmos_devp = kmalloc(sizeof(struct cmos_dev), GFP_KERNEL);
if (!cmos_devp)
{
printk("Bad Kmalloc\n"); return 1;
}
cmosdev_array[i] = cmos_devp;
/* Request I/O region */
sprintf(cmos_devp->name, "cmos%d", i);
if (!(request_region(addrports[i], 2, cmos_devp->name)))
{
printk("cmos: I/O port 0x%x is not free.\n", addrports[i]);
return -EIO;
}
/* Fill in the bank number to correlate this device
* with the corresponding CMOS bank */
cmos_devp->bank_number = i;
/* Connect the file operations with the cdev */
cdev_init(&cmos_devp->cdev, &cmos_fops);
cmos_devp->cdev.owner = THIS_MODULE;
/* Connect the major/minor number to the cdev */
if(cdev_add(&cmos_devp->cdev,(cmos_dev_number + i),1))
{
printk("Bad cdev\n");
return 1;
}
/* Send uevents to udev, so it'll create /dev nodes */
class_device_create(cmos_class, NULL, (cmos_dev_number + i),NULL, "cmos%d", i);
}
printk("CMOS Driver Initialized.\n");
return 0;
}
//clean-up function
/* Driver Exit */
void __exit
cmos_cleanup(void)
{
int i;
/* Release the major number */
unregister_chrdev_region(MAJOR(cmos_dev_number), NUM_CMOS_BANKS);
/* Release I/O region */
for (i=0; i<NUM_CMOS_BANKS; i++)
{
/* Remove the cdev */
cdev_del(&(cmosdev_array[i]->cdev));
class_device_destroy(cmos_class, MKDEV(MAJOR(cmos_dev_number), i));
release_region(addrports[i], 2);
kfree(cmosdev_array[i]);
}
/* Destroy cmos_class */
class_destroy(cmos_class);
return;
}
Please provide me any feedback on this piece of code.
This issue is resolved, problem is indeed in my driver cleanup function.
unregister_chrdev_region(
MAJOR(cmos_dev_number), NUM_CMOS_BANKS);
Instead of passing MAJOR(cmos_dev_number) passing 'cmod_dev_number' works.But still i an not able to figure out that how chrdevs[i] (in fs/char_dev.c) is getting NULL in unregister_chrdev_region
> Thanks,
> Chetan Nanda
>
--
Regards,
Sandeep.
"To learn is to change. Education is a process that changes the learner."
