[06/36] cpuidle: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

This allows us to clean up the cpuidle_add_interface() call a bit as it
was only called in one place, with the same argument so just put that
into the function itself.  Note that cpuidle_remove_interface() should
also probably be removed in the future as there are no callers of it for
some reason.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Note, this is a patch that is a prepatory cleanup as part of a larger
series of patches that is working on resolving some old driver core
design mistakes.  It will build and apply cleanly on top of 6.3-rc2 on
its own, but I'd prefer if I could take it through my driver-core tree
so that the driver core changes can be taken through there for 6.4-rc1.

 drivers/cpuidle/cpuidle.c |  2 +-
 drivers/cpuidle/cpuidle.h |  2 +-
 drivers/cpuidle/sysfs.c   | 12 +++++++++---
 3 files changed, 11 insertions(+), 5 deletions(-)

On Mon, Mar 13, 2023 at 07:58:02PM +0100, Rafael J. Wysocki wrote:
> On Mon, Mar 13, 2023 at 7:30 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > Direct access to the struct bus_type dev_root pointer is going away soon
> > so replace that with a call to bus_get_dev_root() instead, which is what
> > it is there for.
> >
> > This allows us to clean up the cpuidle_add_interface() call a bit as it
> > was only called in one place, with the same argument so just put that
> > into the function itself.  Note that cpuidle_remove_interface() should
> > also probably be removed in the future as there are no callers of it for
> > some reason.
> >
> > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> > Cc: linux-pm@vger.kernel.org
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> > Note, this is a patch that is a prepatory cleanup as part of a larger
> > series of patches that is working on resolving some old driver core
> > design mistakes.  It will build and apply cleanly on top of 6.3-rc2 on
> > its own, but I'd prefer if I could take it through my driver-core tree
> > so that the driver core changes can be taken through there for 6.4-rc1.
> >
> >  drivers/cpuidle/cpuidle.c |  2 +-
> >  drivers/cpuidle/cpuidle.h |  2 +-
> >  drivers/cpuidle/sysfs.c   | 12 +++++++++---
> >  3 files changed, 11 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> > index 0b00f21cefe3..8e929f6602ce 100644
> > --- a/drivers/cpuidle/cpuidle.c
> > +++ b/drivers/cpuidle/cpuidle.c
> > @@ -808,7 +808,7 @@ static int __init cpuidle_init(void)
> >         if (cpuidle_disabled())
> >                 return -ENODEV;
> >
> > -       return cpuidle_add_interface(cpu_subsys.dev_root);
> > +       return cpuidle_add_interface();
> >  }
> >
> >  module_param(off, int, 0444);
> > diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
> > index 9f336af17fa6..52701d9588f1 100644
> > --- a/drivers/cpuidle/cpuidle.h
> > +++ b/drivers/cpuidle/cpuidle.h
> > @@ -30,7 +30,7 @@ extern int cpuidle_switch_governor(struct cpuidle_governor *gov);
> >
> >  struct device;
> >
> > -extern int cpuidle_add_interface(struct device *dev);
> > +extern int cpuidle_add_interface(void);
> >  extern void cpuidle_remove_interface(struct device *dev);
> >  extern int cpuidle_add_device_sysfs(struct cpuidle_device *device);
> >  extern void cpuidle_remove_device_sysfs(struct cpuidle_device *device);
> > diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
> > index 48948b171749..84e4946f1072 100644
> > --- a/drivers/cpuidle/sysfs.c
> > +++ b/drivers/cpuidle/sysfs.c
> > @@ -119,11 +119,17 @@ static struct attribute_group cpuidle_attr_group = {
> >
> >  /**
> >   * cpuidle_add_interface - add CPU global sysfs attributes
> > - * @dev: the target device
> >   */
> > -int cpuidle_add_interface(struct device *dev)
> > +int cpuidle_add_interface(void)
> >  {
> > -       return sysfs_create_group(&dev->kobj, &cpuidle_attr_group);
> > +       struct device *dev_root = bus_get_dev_root(&cpu_subsys);
> > +       int retval = -EINVAL;
> > +
> > +       if (dev_root) {
> > +               retval = sysfs_create_group(&dev_root->kobj, &cpuidle_attr_group);
> > +               put_device(dev_root);
> > +       }
> > +       return retval;
> 
> I would prefer
> 
>   if (!dev_root)
>           return -EINVAL;
> 
>   retval = sysfs_create_group(&dev_root->kobj, &cpuidle_attr_group);
>   put_device(dev_root);
>   return retval;
> 
> assuming that successful group creation will bump up the reference
> counter of dev_root.

That is correct.  I'll respin this with this change in it now, thanks
for the review!

greg k-h