I meant at BOOT time.
On Sat, Dec 13, 2008 at 4:13 PM, Sandeep K Sinha
<sandeepksinha@xxxxxxxxx> wrote:
> May be at time itself the kernel confirms all the registered devices
> and assign NULL to all remaining.
> Not sure, but will figure that out from the code for sure.
>
> On Sat, Dec 13, 2008 at 1:32 PM, Chetan Nanda <chetannanda@xxxxxxxxx> wrote:
>>
>>
>> On Tue, Dec 9, 2008 at 11:34 AM, Chetan Nanda <chetannanda@xxxxxxxxx> wrote:
>>>
>>>
>>> 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:
>>>> > 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.
>>>>
>>>> /* temporary */
>>>> 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
>>>> >
>>>> > 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[].
>>>> >
>>>>
>>>> Thats right, it is like that.
>>>> 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."
>>>
>>
>>
>
>
>
> --
> Regards,
> Sandeep.
>
>
>
>
>
>
> "To learn is to change. Education is a process that changes the learner."
>
--
Regards,
Sandeep.
"To learn is to change. Education is a process that changes the learner."
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