Subject: Re: [PATCH v4 3/8] mfd: syscon: Add reference counting and device managed support

From: Herve Codina <[email-masked]>
Date: Wed, 7 Aug 2024 15:29:27 +0200

Hi Andy,

On Mon, 5 Aug 2024 22:20:56 +0200
Andy Shevchenko <[email-masked]> wrote:

> On Mon, Aug 5, 2024 at 12:19 PM Herve Codina <[email-masked]> wrote:
> >
> > From: Clément Léger <[email-masked]>
> >
> > Syscon releasing is not supported.
> > Without release function, unbinding a driver that uses syscon whether
> > explicitly or due to a module removal left the used syscon in a in-use
> > state.
> >
> > For instance a syscon_node_to_regmap() call from a consumer retrieve a  
> 
> retrieves?

Indeed, will be fixed.

> 
> > syscon regmap instance. Internally, syscon_node_to_regmap() can create
> > syscon instance and add it to the existing syscon list. No API is
> > available to release this syscon instance, remove it from the list and
> > free it when it is not used anymore.
> >
> > Introduce reference counting in syscon in order to keep track of syscon
> > usage using syscon_{get,put}() and add a device managed version of
> > syscon_regmap_lookup_by_phandle(), to automatically release the syscon
> > instance on the consumer removal.  
> 
> ...
> 
> > -       if (!syscon)
> > +       if (!syscon) {
> >                 syscon = of_syscon_register(np, check_res);
> > +               if (IS_ERR(syscon))
> > +                       return ERR_CAST(syscon);
> > +       } else {
> > +               syscon_get(syscon);
> > +       }  
> 
>   if (syscon)
>     return syscon_get();
> 
> ?
> 
> > +       return syscon;  

Yes and further more, I will remove also the unneeded IS_ERR() and ERR_CAST().
This will lead to just:

	if (syscon)
		return syscon_get(syscon);

	return of_syscon_register(np, check_res);

> 
> ...
> 
> > +static struct regmap *__devm_syscon_get(struct device *dev,
> > +                                       struct syscon *syscon)
> > +{
> > +       struct syscon **ptr;
> > +
> > +       if (IS_ERR(syscon))
> > +               return ERR_CAST(syscon);
> > +
> > +       ptr = devres_alloc(devm_syscon_release, sizeof(struct syscon *), GFP_KERNEL);
> > +       if (!ptr) {
> > +               syscon_put(syscon);
> > +               return ERR_PTR(-ENOMEM);
> > +       }
> > +
> > +       *ptr = syscon;
> > +       devres_add(dev, ptr);
> > +
> > +       return syscon->regmap;  
> 
> Can't the devm_add_action_or_reset() be used in this case? If so,
> perhaps a comment to explain why?

There is no reason to avoid the use of devm_add_action_or_reset() here.
So, I will use it in the next iteration.

Thanks for your review.

Best regards,
Hervé