[PATCH] PM: runtime: Simplify __rpm_get_callback()

[PATCH] PM: runtime: Simplify __rpm_get_callback()

[Bjorn Helgaas]

From: Bjorn Helgaas <bhelgaas@google.com>

Simplify __rpm_get_callback() slightly by returning as soon as the return
value is known.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/base/power/runtime.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 50e726b6c2cf..7171ed0668f3 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
 
 static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
 {
-	pm_callback_t cb;
-	const struct dev_pm_ops *ops;
+	const struct dev_pm_ops *ops = NULL;
 
 	if (dev->pm_domain)
 		ops = &dev->pm_domain->ops;
@@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
 		ops = dev->class->pm;
 	else if (dev->bus && dev->bus->pm)
 		ops = dev->bus->pm;
-	else
-		ops = NULL;
 
 	if (ops)
-		cb = *(pm_callback_t *)((void *)ops + cb_offset);
-	else
-		cb = NULL;
+		return *(pm_callback_t *)((void *)ops + cb_offset);
 
-	if (!cb && dev->driver && dev->driver->pm)
-		cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
+	if (dev->driver && dev->driver->pm)
+		return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
 
-	return cb;
+	return NULL;
 }
 
 #define RPM_GET_CALLBACK(dev, callback) \
-- 
2.25.1

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Rafael J. Wysocki]

On Thu, Dec 15, 2022 at 7:19 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> From: Bjorn Helgaas <bhelgaas@google.com>
>
> Simplify __rpm_get_callback() slightly by returning as soon as the return
> value is known.  No functional change intended.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
>  drivers/base/power/runtime.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 50e726b6c2cf..7171ed0668f3 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
>
>  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
>  {
> -       pm_callback_t cb;
> -       const struct dev_pm_ops *ops;
> +       const struct dev_pm_ops *ops = NULL;
>
>         if (dev->pm_domain)
>                 ops = &dev->pm_domain->ops;
> @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
>                 ops = dev->class->pm;
>         else if (dev->bus && dev->bus->pm)
>                 ops = dev->bus->pm;
> -       else
> -               ops = NULL;
>
>         if (ops)
> -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> -       else
> -               cb = NULL;
> +               return *(pm_callback_t *)((void *)ops + cb_offset);
>
> -       if (!cb && dev->driver && dev->driver->pm)
> -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> +       if (dev->driver && dev->driver->pm)
> +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
>
> -       return cb;
> +       return NULL;
>  }
>
>  #define RPM_GET_CALLBACK(dev, callback) \
> --

Applied as 6.3 material, thanks!

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Geert Uytterhoeven]

Hi Bjorn,

On Thu, Dec 15, 2022 at 7:23 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
>
> Simplify __rpm_get_callback() slightly by returning as soon as the return
> value is known.  No functional change intended.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Thanks for your patch, which is now commit 650bdddb6b311705 ("PM:
runtime: Simplify __rpm_get_callback()") in pm/linux-next.

> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
>
>  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
>  {
> -       pm_callback_t cb;
> -       const struct dev_pm_ops *ops;
> +       const struct dev_pm_ops *ops = NULL;
>
>         if (dev->pm_domain)
>                 ops = &dev->pm_domain->ops;
> @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
>                 ops = dev->class->pm;
>         else if (dev->bus && dev->bus->pm)
>                 ops = dev->bus->pm;
> -       else
> -               ops = NULL;
>
>         if (ops)
> -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> -       else
> -               cb = NULL;
> +               return *(pm_callback_t *)((void *)ops + cb_offset);

This is a change in behavior in case the callback turns out to be NULL:
  - before, it would fall back to the driver-specific callback below,
  - after, it always returns NULL.

>
> -       if (!cb && dev->driver && dev->driver->pm)
> -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> +       if (dev->driver && dev->driver->pm)
> +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
>
> -       return cb;
> +       return NULL;
>  }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Rafael J. Wysocki]

On Tue, Jan 24, 2023 at 12:20 PM Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
>
> Hi Bjorn,
>
> On Thu, Dec 15, 2022 at 7:23 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > From: Bjorn Helgaas <bhelgaas@google.com>
> >
> > Simplify __rpm_get_callback() slightly by returning as soon as the return
> > value is known.  No functional change intended.
> >
> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>
> Thanks for your patch, which is now commit 650bdddb6b311705 ("PM:
> runtime: Simplify __rpm_get_callback()") in pm/linux-next.
>
> > --- a/drivers/base/power/runtime.c
> > +++ b/drivers/base/power/runtime.c
> > @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
> >
> >  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> >  {
> > -       pm_callback_t cb;
> > -       const struct dev_pm_ops *ops;
> > +       const struct dev_pm_ops *ops = NULL;
> >
> >         if (dev->pm_domain)
> >                 ops = &dev->pm_domain->ops;
> > @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> >                 ops = dev->class->pm;
> >         else if (dev->bus && dev->bus->pm)
> >                 ops = dev->bus->pm;
> > -       else
> > -               ops = NULL;
> >
> >         if (ops)
> > -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > -       else
> > -               cb = NULL;
> > +               return *(pm_callback_t *)((void *)ops + cb_offset);
>
> This is a change in behavior in case the callback turns out to be NULL:
>   - before, it would fall back to the driver-specific callback below,
>   - after, it always returns NULL.

Good point and sorry for missing this!

> >
> > -       if (!cb && dev->driver && dev->driver->pm)
> > -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > +       if (dev->driver && dev->driver->pm)
> > +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> >
> > -       return cb;
> > +       return NULL;
> >  }
>

Something like the patch below (modulo gmail-induced whitespace
breakage) should restore the previous behavior if I'm not mistaken:

---
 drivers/base/power/runtime.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/base/power/runtime.c
===================================================================
--- linux-pm.orig/drivers/base/power/runtime.c
+++ linux-pm/drivers/base/power/runtime.c
@@ -31,8 +31,13 @@ static pm_callback_t __rpm_get_callback(
     else if (dev->bus && dev->bus->pm)
         ops = dev->bus->pm;

-    if (ops)
-        return *(pm_callback_t *)((void *)ops + cb_offset);
+    if (ops) {
+        pm_callback_t cb;
+
+        cb = *(pm_callback_t *)((void *)ops + cb_offset);
+        if (cb)
+            return cb;
+    }

     if (dev->driver && dev->driver->pm)
         return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Geert Uytterhoeven]

Hi Rafael,

On Tue, Jan 24, 2023 at 3:18 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> On Tue, Jan 24, 2023 at 12:20 PM Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
> >
> > Hi Bjorn,
> >
> > On Thu, Dec 15, 2022 at 7:23 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > From: Bjorn Helgaas <bhelgaas@google.com>
> > >
> > > Simplify __rpm_get_callback() slightly by returning as soon as the return
> > > value is known.  No functional change intended.
> > >
> > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> >
> > Thanks for your patch, which is now commit 650bdddb6b311705 ("PM:
> > runtime: Simplify __rpm_get_callback()") in pm/linux-next.
> >
> > > --- a/drivers/base/power/runtime.c
> > > +++ b/drivers/base/power/runtime.c
> > > @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
> > >
> > >  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > >  {
> > > -       pm_callback_t cb;
> > > -       const struct dev_pm_ops *ops;
> > > +       const struct dev_pm_ops *ops = NULL;
> > >
> > >         if (dev->pm_domain)
> > >                 ops = &dev->pm_domain->ops;
> > > @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > >                 ops = dev->class->pm;
> > >         else if (dev->bus && dev->bus->pm)
> > >                 ops = dev->bus->pm;
> > > -       else
> > > -               ops = NULL;
> > >
> > >         if (ops)
> > > -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > > -       else
> > > -               cb = NULL;
> > > +               return *(pm_callback_t *)((void *)ops + cb_offset);
> >
> > This is a change in behavior in case the callback turns out to be NULL:
> >   - before, it would fall back to the driver-specific callback below,
> >   - after, it always returns NULL.
>
> Good point and sorry for missing this!
>
> > >
> > > -       if (!cb && dev->driver && dev->driver->pm)
> > > -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > +       if (dev->driver && dev->driver->pm)
> > > +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > >
> > > -       return cb;
> > > +       return NULL;
> > >  }
> >
>
> Something like the patch below (modulo gmail-induced whitespace
> breakage) should restore the previous behavior if I'm not mistaken:
>
> ---
>  drivers/base/power/runtime.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -31,8 +31,13 @@ static pm_callback_t __rpm_get_callback(
>      else if (dev->bus && dev->bus->pm)
>          ops = dev->bus->pm;
>
> -    if (ops)
> -        return *(pm_callback_t *)((void *)ops + cb_offset);
> +    if (ops) {
> +        pm_callback_t cb;
> +
> +        cb = *(pm_callback_t *)((void *)ops + cb_offset);
> +        if (cb)
> +            return cb;
> +    }
>
>      if (dev->driver && dev->driver->pm)
>          return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);

Which is now more complex than the original?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Rafael J. Wysocki]

On Tue, Jan 24, 2023 at 3:37 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Rafael,
>
> On Tue, Jan 24, 2023 at 3:18 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > On Tue, Jan 24, 2023 at 12:20 PM Geert Uytterhoeven
> > <geert@linux-m68k.org> wrote:
> > >
> > > Hi Bjorn,
> > >
> > > On Thu, Dec 15, 2022 at 7:23 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > >
> > > > Simplify __rpm_get_callback() slightly by returning as soon as the return
> > > > value is known.  No functional change intended.
> > > >
> > > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > >
> > > Thanks for your patch, which is now commit 650bdddb6b311705 ("PM:
> > > runtime: Simplify __rpm_get_callback()") in pm/linux-next.
> > >
> > > > --- a/drivers/base/power/runtime.c
> > > > +++ b/drivers/base/power/runtime.c
> > > > @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
> > > >
> > > >  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > > >  {
> > > > -       pm_callback_t cb;
> > > > -       const struct dev_pm_ops *ops;
> > > > +       const struct dev_pm_ops *ops = NULL;
> > > >
> > > >         if (dev->pm_domain)
> > > >                 ops = &dev->pm_domain->ops;
> > > > @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > > >                 ops = dev->class->pm;
> > > >         else if (dev->bus && dev->bus->pm)
> > > >                 ops = dev->bus->pm;
> > > > -       else
> > > > -               ops = NULL;
> > > >
> > > >         if (ops)
> > > > -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > > > -       else
> > > > -               cb = NULL;
> > > > +               return *(pm_callback_t *)((void *)ops + cb_offset);
> > >
> > > This is a change in behavior in case the callback turns out to be NULL:
> > >   - before, it would fall back to the driver-specific callback below,
> > >   - after, it always returns NULL.
> >
> > Good point and sorry for missing this!
> >
> > > >
> > > > -       if (!cb && dev->driver && dev->driver->pm)
> > > > -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > > +       if (dev->driver && dev->driver->pm)
> > > > +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > >
> > > > -       return cb;
> > > > +       return NULL;
> > > >  }
> > >
> >
> > Something like the patch below (modulo gmail-induced whitespace
> > breakage) should restore the previous behavior if I'm not mistaken:
> >
> > ---
> >  drivers/base/power/runtime.c |    9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > Index: linux-pm/drivers/base/power/runtime.c
> > ===================================================================
> > --- linux-pm.orig/drivers/base/power/runtime.c
> > +++ linux-pm/drivers/base/power/runtime.c
> > @@ -31,8 +31,13 @@ static pm_callback_t __rpm_get_callback(
> >      else if (dev->bus && dev->bus->pm)
> >          ops = dev->bus->pm;
> >
> > -    if (ops)
> > -        return *(pm_callback_t *)((void *)ops + cb_offset);
> > +    if (ops) {
> > +        pm_callback_t cb;
> > +
> > +        cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > +        if (cb)
> > +            return cb;
> > +    }
> >
> >      if (dev->driver && dev->driver->pm)
> >          return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
>
> Which is now more complex than the original?

Arguably so.

OK, I'll drop the commit in question then, sorry Bjorn.

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Bjorn Helgaas]

On Tue, Jan 24, 2023 at 03:45:50PM +0100, Rafael J. Wysocki wrote:
> On Tue, Jan 24, 2023 at 3:37 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > On Tue, Jan 24, 2023 at 3:18 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > On Tue, Jan 24, 2023 at 12:20 PM Geert Uytterhoeven
> > > <geert@linux-m68k.org> wrote:
> > > > On Thu, Dec 15, 2022 at 7:23 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > > >
> > > > > Simplify __rpm_get_callback() slightly by returning as soon as the return
> > > > > value is known.  No functional change intended.
> > > > >
> > > > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > > >
> > > > Thanks for your patch, which is now commit 650bdddb6b311705 ("PM:
> > > > runtime: Simplify __rpm_get_callback()") in pm/linux-next.
> > > >
> > > > > --- a/drivers/base/power/runtime.c
> > > > > +++ b/drivers/base/power/runtime.c
> > > > > @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
> > > > >
> > > > >  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > > > >  {
> > > > > -       pm_callback_t cb;
> > > > > -       const struct dev_pm_ops *ops;
> > > > > +       const struct dev_pm_ops *ops = NULL;
> > > > >
> > > > >         if (dev->pm_domain)
> > > > >                 ops = &dev->pm_domain->ops;
> > > > > @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > > > >                 ops = dev->class->pm;
> > > > >         else if (dev->bus && dev->bus->pm)
> > > > >                 ops = dev->bus->pm;
> > > > > -       else
> > > > > -               ops = NULL;
> > > > >
> > > > >         if (ops)
> > > > > -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > > > > -       else
> > > > > -               cb = NULL;
> > > > > +               return *(pm_callback_t *)((void *)ops + cb_offset);
> > > >
> > > > This is a change in behavior in case the callback turns out to be NULL:
> > > >   - before, it would fall back to the driver-specific callback below,
> > > >   - after, it always returns NULL.
> > >
> > > Good point and sorry for missing this!
> > >
> > > > >
> > > > > -       if (!cb && dev->driver && dev->driver->pm)
> > > > > -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > > > +       if (dev->driver && dev->driver->pm)
> > > > > +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > > >
> > > > > -       return cb;
> > > > > +       return NULL;
> > > > >  }
> > > >
> > >
> > > Something like the patch below (modulo gmail-induced whitespace
> > > breakage) should restore the previous behavior if I'm not mistaken:
> > >
> > > ---
> > >  drivers/base/power/runtime.c |    9 +++++++--
> > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > >
> > > Index: linux-pm/drivers/base/power/runtime.c
> > > ===================================================================
> > > --- linux-pm.orig/drivers/base/power/runtime.c
> > > +++ linux-pm/drivers/base/power/runtime.c
> > > @@ -31,8 +31,13 @@ static pm_callback_t __rpm_get_callback(
> > >      else if (dev->bus && dev->bus->pm)
> > >          ops = dev->bus->pm;
> > >
> > > -    if (ops)
> > > -        return *(pm_callback_t *)((void *)ops + cb_offset);
> > > +    if (ops) {
> > > +        pm_callback_t cb;
> > > +
> > > +        cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > > +        if (cb)
> > > +            return cb;
> > > +    }
> > >
> > >      if (dev->driver && dev->driver->pm)
> > >          return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> >
> > Which is now more complex than the original?
> 
> Arguably so.
> 
> OK, I'll drop the commit in question then, sorry Bjorn.

Really sorry about this.  Think I'm all out of brown paper bags :(
Thanks for catching this, Geert, and sorry for all the time you had to
spend debugging it.

Bjorn

Re: [PATCH] PM: runtime: Simplify __rpm_get_callback()

[Geert Uytterhoeven]

Hi Bjorn,

On Tue, Jan 24, 2023 at 4:06 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Tue, Jan 24, 2023 at 03:45:50PM +0100, Rafael J. Wysocki wrote:
> > On Tue, Jan 24, 2023 at 3:37 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > On Tue, Jan 24, 2023 at 3:18 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > > On Tue, Jan 24, 2023 at 12:20 PM Geert Uytterhoeven
> > > > <geert@linux-m68k.org> wrote:
> > > > > On Thu, Dec 15, 2022 at 7:23 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > > > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > > > >
> > > > > > Simplify __rpm_get_callback() slightly by returning as soon as the return
> > > > > > value is known.  No functional change intended.
> > > > > >
> > > > > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > > > >
> > > > > Thanks for your patch, which is now commit 650bdddb6b311705 ("PM:
> > > > > runtime: Simplify __rpm_get_callback()") in pm/linux-next.
> > > > >
> > > > > > --- a/drivers/base/power/runtime.c
> > > > > > +++ b/drivers/base/power/runtime.c
> > > > > > @@ -20,8 +20,7 @@ typedef int (*pm_callback_t)(struct device *);
> > > > > >
> > > > > >  static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > > > > >  {
> > > > > > -       pm_callback_t cb;
> > > > > > -       const struct dev_pm_ops *ops;
> > > > > > +       const struct dev_pm_ops *ops = NULL;
> > > > > >
> > > > > >         if (dev->pm_domain)
> > > > > >                 ops = &dev->pm_domain->ops;
> > > > > > @@ -31,18 +30,14 @@ static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
> > > > > >                 ops = dev->class->pm;
> > > > > >         else if (dev->bus && dev->bus->pm)
> > > > > >                 ops = dev->bus->pm;
> > > > > > -       else
> > > > > > -               ops = NULL;
> > > > > >
> > > > > >         if (ops)
> > > > > > -               cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > > > > > -       else
> > > > > > -               cb = NULL;
> > > > > > +               return *(pm_callback_t *)((void *)ops + cb_offset);
> > > > >
> > > > > This is a change in behavior in case the callback turns out to be NULL:
> > > > >   - before, it would fall back to the driver-specific callback below,
> > > > >   - after, it always returns NULL.
> > > >
> > > > Good point and sorry for missing this!
> > > >
> > > > > >
> > > > > > -       if (!cb && dev->driver && dev->driver->pm)
> > > > > > -               cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > > > > +       if (dev->driver && dev->driver->pm)
> > > > > > +               return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > > > > >
> > > > > > -       return cb;
> > > > > > +       return NULL;
> > > > > >  }
> > > > >
> > > >
> > > > Something like the patch below (modulo gmail-induced whitespace
> > > > breakage) should restore the previous behavior if I'm not mistaken:
> > > >
> > > > ---
> > > >  drivers/base/power/runtime.c |    9 +++++++--
> > > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > > >
> > > > Index: linux-pm/drivers/base/power/runtime.c
> > > > ===================================================================
> > > > --- linux-pm.orig/drivers/base/power/runtime.c
> > > > +++ linux-pm/drivers/base/power/runtime.c
> > > > @@ -31,8 +31,13 @@ static pm_callback_t __rpm_get_callback(
> > > >      else if (dev->bus && dev->bus->pm)
> > > >          ops = dev->bus->pm;
> > > >
> > > > -    if (ops)
> > > > -        return *(pm_callback_t *)((void *)ops + cb_offset);
> > > > +    if (ops) {
> > > > +        pm_callback_t cb;
> > > > +
> > > > +        cb = *(pm_callback_t *)((void *)ops + cb_offset);
> > > > +        if (cb)
> > > > +            return cb;
> > > > +    }
> > > >
> > > >      if (dev->driver && dev->driver->pm)
> > > >          return *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
> > >
> > > Which is now more complex than the original?
> >
> > Arguably so.
> >
> > OK, I'll drop the commit in question then, sorry Bjorn.
>
> Really sorry about this.  Think I'm all out of brown paper bags :(
> Thanks for catching this, Geert, and sorry for all the time you had to

Np, no time was wasted on debugging.
I just noticed because I have some local debug code on top, which no
longer applied 8^)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds