On Mon, Oct 01, 2012 at 07:30:38AM +0200, Arun MURTHY wrote:
> > On Fri, Sep 28, 2012 at 01:35:01PM +0530, Arun Murthy wrote:
> > > +#include <linux/module.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/err.h>
> > > +#include <linux/printk.h>
> > > +#include <linux/modem_shm/modem.h>
> > > +
> > > +static struct class *modem_class;
> >
> > What's wrong with a bus_type instead?
>
> Can I know the advantage of using bus_type over class?
You have devices living on a bus, and it's much more descriptive than a
class (which we are going to eventually get rid of one of these
days...).
Might I ask why you choose a class over a bus_type?
> > > +int modem_release(struct modem_desc *mdesc) {
> > > + if (!mdesc->release)
> > > + return -EFAULT;
> > > +
> > > + if (modem_is_requested(mdesc)) {
> > > + atomic_dec(&mdesc->mclients->cnt);
> > > + if (atomic_read(&mdesc->use_cnt) == 1) {
> > > + mdesc->release(mdesc);
> > > + atomic_dec(&mdesc->use_cnt);
> > > + }
> >
> > Eeek, why aren't you using the built-in reference counting that the struct
> > device provided to you, and instead are rolling your own? This happens in
> > many places, why?
>
> My usage of counters over here is for each modem there are many clients.
> Each of the clients will have a ref to modem_desc. Each of them use this for
> requesting and releasing the modem. One counter for tracking the request
> and release for each client which is done by variable 'cnt' in struct clients.
> The counter use_cnt is used for tracking the modem request/release
> irrespective
> of the clients and counter cli_cnt is used for restricting the modem_get to
> the no of clients defined in no_clients.
>
> So totally 3 counter one for restricting the usage of modem_get by clients,
> second for restricting modem request/release at top level, and 3rd for
> restricting modem release/request for per client per modem basis.
>
> Can you let me know if the same can be achieved by using built-in ref
> counting?
Yes, because you don't need all of those different levels, just stick
with one and you should be fine. :)
thanks,
greg k-h
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