Sysfs class attribute problem
Jeshwanth Kumar N K Jeshu
jeshkumar555 at gmail.com
Thu Jun 21 14:28:49 EDT 2012
Hello Anish
Thank you for the changes. Ya now I understoor dealing with store function.
:)
And I did small change in ur code.
I have declared the show and store function as I declared before.
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);
instead.
static ssize_t attr1_store(struct class *cls, const char *buf, size_t
count);
static ssize_t attr1_show(struct class *cls, char *buf);
After this its working fine.
On Thu, Jun 21, 2012 at 9:04 AM, anish singh <anish198519851985 at gmail.com>wrote:
> On Wed, Jun 20, 2012 at 11:32 PM, Jeshwanth Kumar N K Jeshu
> <jeshkumar555 at gmail.com> wrote:
> > 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 :)
> #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 = NULL;
> static ssize_t attr1_store(struct class *cls, const char *buf, size_t
> count);
> static ssize_t attr1_show(struct class *cls, char *buf);
>
> static struct class_attribute pwm_class_attrs[] = {
> __ATTR(attr1, 0666, attr1_show, attr1_store), //use macro for
> permission
> __ATTR_NULL
> };
>
> static struct class pwm_class =
> {
> .name = "dev_jes",
> .owner = THIS_MODULE,
> .class_attrs = pwm_class_attrs
> };
>
>
> static int hello_init(void)
> {
> char string[] = "nothing";
> gvar = kmalloc(sizeof(char)*strlen(string), GFP_KERNEL);
> class_register(&pwm_class);
> snprintf(gvar, sizeof(char)*strlen(string)+1, "%s", string);
> printk("anish In hello_init function \n");
> return 0;
> }
>
> static ssize_t attr1_show(struct class *cls, char *buf)
> {
>
> printk("In attr1_show function\n");
> printk("%s\n", gvar);
> printk("In attr1_show function\n");
> return sprintf(buf, "%s", gvar);
> }
>
> static ssize_t attr1_store(struct class *cls, const char *buf, size_t
> count)
> {
> printk("the string is : %s count %d\n", buf, count);
> return snprintf(gvar, count, "%s\n", buf);
> }
>
>
> 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");
> ======================================================
> Hope you got the point.
>
> >
> >
> >
> > 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
> >
>
--
Regards
Jeshwanth Kumar N K
+91-7411483498
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20120621/823ccff0/attachment.html
More information about the Kernelnewbies
mailing list