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Subject: RE: clarity on kref needed.
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Thread-Topic: clarity on kref needed.
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From: "Mukund JB." <mukundjb@esntechnologies.co.in>
To: "Greg KH" <greg@kroah.com>
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> > I have gone through kref and am planning to implement then 
> in my usb driver.
> 
> What kind of usb driver?
It is a finger print authentication USB driver. it doesn ot do the authgentication but transports data to the application which really does some processing.

No, I did not find any Documentation/kref.txt.
But I have read about kred in the link below:
http://developer.osdl.org/dev/robustmutexes/src/fusyn.hg/Documentation/kref.txt

Is kref depricated because I find nothing related to it in linux/Documentation/?

Thanks & Regards,
Mukund Jampala
> 
> > please terminate my misconceptions if any by correcting the 
> statements below.
> > 
> > In the call below:
> > kref_init(&dev->kref);
> > 	sets the refcount in the kref to 1.
> 
> Yes.
> 
> > kref_put(&dev->kref);
> > 	increment the refcount.
> 
> Hm, don't you mean "kref_get()" here?  If so, yes, that is correct.
> 
> > kref_put(&dev->kref, mem_release );
> > What I understand is when the refcount falls back to '1', only then
> > the mem_release() function will be called.
> 
> No, when it falls to 0 it will be called.
> 
> > Is it correct? I mean, when is the mem_release () called 
> i.e. when the
> > refcount is '0' or '1'.
> 
> 0.  There's an OLS paper from a few years ago that describes kref in
> detail, as well as the in-kernel documentation of it (see the file
> Documentation/kref.txt).  Did you read that?
> 
> thanks,
> 
> greg k-h
>