Sysfs class attribute problem

[Jeshwanth Kumar N K Jeshu]

Hello

Thank you anish for the reply, the code is I pasted below.
[code-starts]

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/sysdev.h>
#include <linux/major.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/cdev.h>
#include <linux/kdev_t.h>

static char *gvar = "BeHonest";
// Store and Show functions......
 static ssize_t attr1_store(struct class *cls, struct class_attribute
*attr, const char *buf, size_t count);
 static ssize_t attr1_show(struct class *cls, struct class_attribute *attr,
char *buf);

static struct class_attribute pwm_class_attrs[] = {
    __ATTR(attr1, S_IRUGO | S_IWUSR , attr1_show, attr1_store),
    __ATTR_NULL
};

static struct class pwm_class =
{
    .name = "dev_jes",
    .owner = THIS_MODULE,
    .class_attrs = pwm_class_attrs
};


static int hello_init(void)
{
    class_register(&pwm_class);
    printk("In hello_init function \n");

    return 0;
}

static ssize_t attr1_show(struct class *cls, struct class_attribute *attr,
char *buf)
{

    printk("In attr1_show function\n");
    return sprintf(buf, "%s\n", gvar);
}

static ssize_t attr1_store(struct class *cls, struct class_attribute *attr,
const char *buf, size_t count)
{
            printk("the string is : %s\n",buf);
            printk("In attr1_store function\n");
            return 1;
            //return sprintf(gvar, "%s\n", buf);  --- If I put this line I
am getting ERROR :(
}


static void  hello_exit(void)
{
    class_unregister(&pwm_class);
    printk("In hello_exit function \n");
}

module_init(hello_init);
module_exit(hello_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jeshwanth");
MODULE_DESCRIPTION("Learning sysfs");

[code-ends]

echo "jeshu" > /sys/class/dev_jes/attr1

And If I pass the command to atttribute I got result below in dmesg.

[ 3435.613057] the string is : jeshu
[ 3435.613061]
[ 3435.613066] In attr1_store function
[ 3435.613072] the string is : eshu
[ 3435.613074]
[ 3435.613078] In attr1_store function
[ 3435.613083] the string is : shu
[ 3435.613085]
[ 3435.613088] In attr1_store function
[ 3435.613093] the string is : hu
[ 3435.613095]
[ 3435.613098] In attr1_store function
[ 3435.613103] the string is : u
[ 3435.613105]
[ 3435.613108] In attr1_store function
[ 3435.613113] the string is :
[ 3435.613115]
[ 3435.613118] In attr1_store function


So please help me how to read the attribute in store function.. Thanks :)


On Tue, Jun 19, 2012 at 4:02 PM, anish singh <anish198519851985 at gmail.com>wrote:

> On Tue, Jun 19, 2012 at 3:14 PM, jeshwanth Kumar N K
> <jeshkumar555 at gmail.com> wrote:
> > Hello all
> >
> > I am new to sysfs interface ans I read about in mochel's documentation.
> And
> > doing some experiements on it. Let's come to Tue problem, in my module I
> > have a global variable type char* myglobal and it s static, I am putting
> > that value in my one and only class attribute using show function. But
> for
> > the same if I a user put some value in to the using echo or something,
> the
> > attribute value is not changing. And one more thing s after I passed the
> > value to the attribute my system not shutting down :( . Please help me
> how
> > to read values.
> Why don't you post your code?As that will really help and moreover as
> this is your code
> you won't be breakign any law set by your company.
> >
> > // in store function I am doing this:
> > Myglobal = bus;
> >
> > Sent from my HTC
> >
> >
> >
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
>



-- 
Regards
Jeshwanth Kumar N K
+91-7411483498
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