issues dealing with kobjects

Raghavendra arrao at cdac.in
Fri Jun 20 02:01:03 EDT 2014


Hello all,

I am facing a small issue dealing with kobjects.
I am writing a simple i2c driver for which I would like to export a few 
sysfs attributes(files).
The files are many, so I've decided to pack them into a directory in 
sysfs (inside the i2c device) and so I thought of kobjects.

My private data struture is something like this :
struct my_private {
     struct i2c_client *client;
     ...
     struct kobject kobj;
};

In my probe function, I am doing something like this :
int my_probe(struct i2c_client *client, ...)
{
     struct my_private *dev;

     dev = devm_kzalloc(...);
     pr_info("%x", dev);                    /* The address that I got is 
: 0xdbf94210 */

     ....

     /* Init. and add kboject */
     kobject_init(&dev->kobj, client->dev.kobj.ktype);
     kobject_add(&dev->kobj, &client->dev.kobj, "my_dir");

     /* Export sysfs group */
     sysfs_create_group(&dev->kobj, &my_attr_grp);

     ....
}

My show function for one of the attribute is something like this :
ssize_t show(struct kobject *kobj, ... )
{
     struct my_private *dev = container_of(kobj, struct my_private, kobj);
     pr_info("%x", dev);                    /* The address that I got is 
: 0xdbf94208 */

     ....
}

I tried to probe and remove the device mutilple times. Every time I am 
getting a difference of 2bytes for the 'dev'
pointer between probe and show functions.

Can anyone explain me where am I going wrong or is there any better way 
to create directories in sysfs?
I am building this module against 3.13.2 kernel.

Thank you.
Raghavendra.



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