Problems with adding a sysfs file

Problems with adding a sysfs file

[Abhishek Bhardwaj]

I followed this link to add a sysfs file
http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/
.

I set the driver.groups field and declared the attribute and attribute
groups required by the sysfs file. When I boot my kernel I see the
file but my store and show handlers don't get called when I try to cat
or echo to the file. Is there any step I'm missing ?. I also see that
a lot of drivers still use sysfs_create_file which is racy according
to the link I posted.

-
AB

Problems with adding a sysfs file

[valdis.kletnieks at vt.edu]

On Mon, 17 Apr 2017 01:17:08 -0700, Abhishek Bhardwaj said:
> I followed this link to add a sysfs file
> http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/
> .
>
> I set the driver.groups field and declared the attribute and attribute
> groups required by the sysfs file. When I boot my kernel I see the
> file but my store and show handlers don't get called when I try to cat
> or echo to the file. Is there any step I'm missing ?.

The traditional way to start debugging this is to add a line at the beginning
of your show and store routines:

	printk(KERN_DEBUG "Now in our special sysfs show routine\n");

and see if it shows up in your dmesg or not.  If not, your routine
is probably not being called.  If it is, the problem is in the routine.

(You'd be surprised how often people say their routine isn't getting called,
when it in fact is, or vice versa..)
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Problems with adding a sysfs file

[Abhishek Bhardwaj]

I used a pr_debug and printk KERN_INFO ,before my original email , to
verify they weren't being called.

On Apr 17, 2017 1:43 PM, <valdis.kletnieks@vt.edu> wrote:

> On Mon, 17 Apr 2017 01:17:08 -0700, Abhishek Bhardwaj said:
> > I followed this link to add a sysfs file
> > http://kroah.com/log/blog/2013/06/26/how-to-create-a-
> sysfs-file-correctly/
> > .
> >
> > I set the driver.groups field and declared the attribute and attribute
> > groups required by the sysfs file. When I boot my kernel I see the
> > file but my store and show handlers don't get called when I try to cat
> > or echo to the file. Is there any step I'm missing ?.
>
> The traditional way to start debugging this is to add a line at the
> beginning
> of your show and store routines:
>
>         printk(KERN_DEBUG "Now in our special sysfs show routine\n");
>
> and see if it shows up in your dmesg or not.  If not, your routine
> is probably not being called.  If it is, the problem is in the routine.
>
> (You'd be surprised how often people say their routine isn't getting
> called,
> when it in fact is, or vice versa..)
>
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Problems with adding a sysfs file

[Tobin C. Harding]

On Mon, Apr 17, 2017 at 02:04:48PM -0700, Abhishek Bhardwaj wrote:
> I used a pr_debug and printk KERN_INFO ,before my original email , to
> verify they weren't being called.

You will have more success on kernel mailing lists if you do not top
post as you have done :)

> On Apr 17, 2017 1:43 PM, <valdis.kletnieks@vt.edu> wrote:
> 
> > On Mon, 17 Apr 2017 01:17:08 -0700, Abhishek Bhardwaj said:
> > > I followed this link to add a sysfs file
> > > http://kroah.com/log/blog/2013/06/26/how-to-create-a-
> > sysfs-file-correctly/
> > > .
> > >
> > > I set the driver.groups field and declared the attribute and attribute
> > > groups required by the sysfs file. When I boot my kernel I see the
> > > file but my store and show handlers don't get called when I try to cat
> > > or echo to the file. Is there any step I'm missing ?.
> >
> > The traditional way to start debugging this is to add a line at the
> > beginning
> > of your show and store routines:
> >
> >         printk(KERN_DEBUG "Now in our special sysfs show routine\n");

You could have put your response here, that way readers would have a
reference to you comment.

> > and see if it shows up in your dmesg or not.  If not, your routine
> > is probably not being called.  If it is, the problem is in the routine.
> >
> > (You'd be surprised how often people say their routine isn't getting
> > called,
> > when it in fact is, or vice versa..)
> >

Good luck,
Tobin.