[PATCH] i2c: i801: mark PM functions as __maybe_unused

[PATCH] i2c: i801: mark PM functions as __maybe_unused

[Anders Roxell]

With CONFIG_PM, we get a harmless build warning:
drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
 static int i801_resume(struct device *dev)
            ^~~~~~~~~~~
drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
 static int i801_suspend(struct device *dev)
            ^~~~~~~~~~~~

This marks the affected functions as __maybe_unused.

Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 drivers/i2c/busses/i2c-i801.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index ed07f9002710..ff18c6ed2bec 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1711,7 +1711,7 @@ static void i801_shutdown(struct pci_dev *dev)
 }
 
 #ifdef CONFIG_PM
-static int i801_suspend(struct device *dev)
+static int __maybe_unused i801_suspend(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct i801_priv *priv = pci_get_drvdata(pci_dev);
@@ -1720,7 +1720,7 @@ static int i801_suspend(struct device *dev)
 	return 0;
 }
 
-static int i801_resume(struct device *dev)
+static int __maybe_unused i801_resume(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct i801_priv *priv = pci_get_drvdata(pci_dev);
-- 
2.17.0

Re: [PATCH] i2c: i801: mark PM functions as __maybe_unused

[Jean Delvare]

Hi Anders,

On Tue,  8 May 2018 09:38:52 +0200, Anders Roxell wrote:
> With CONFIG_PM, we get a harmless build warning:
> drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
>  static int i801_resume(struct device *dev)
>             ^~~~~~~~~~~
> drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
>  static int i801_suspend(struct device *dev)
>             ^~~~~~~~~~~~

I have CONFIG_PM=y and I don't get this warning, even with W=1. Which
gcc version are you using, which exact kernel version are you building,
and what is the value of all the CONFIG_PM_* options?

> This marks the affected functions as __maybe_unused.

I'm not a big fan of __maybe_unused, at least not in this specific
situation. We should be able to know exactly when these functions are
needed, and only include them when this is the case. Building unused
code just to discard it later (hopefully?) is a waste of CPU time.

> 
> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")

If SIMPLE_DEV_PM_OPS causes it but UNIVERSAL_DEV_PM_OPS did not, I
suppose that what matters is CONFIG_PM_SLEEP.

So maybe we can just replace "#ifdef CONFIG_PM" with "ifdef
CONFIG_PM_SLEEP" in the code below?

> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
> ---
>  drivers/i2c/busses/i2c-i801.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index ed07f9002710..ff18c6ed2bec 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -1711,7 +1711,7 @@ static void i801_shutdown(struct pci_dev *dev)
>  }
>  
>  #ifdef CONFIG_PM
> -static int i801_suspend(struct device *dev)
> +static int __maybe_unused i801_suspend(struct device *dev)
>  {
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	struct i801_priv *priv = pci_get_drvdata(pci_dev);
> @@ -1720,7 +1720,7 @@ static int i801_suspend(struct device *dev)
>  	return 0;
>  }
>  
> -static int i801_resume(struct device *dev)
> +static int __maybe_unused i801_resume(struct device *dev)
>  {
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	struct i801_priv *priv = pci_get_drvdata(pci_dev);


-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH] i2c: i801: mark PM functions as __maybe_unused

[Jean Delvare]

On Wed, 9 May 2018 19:00:55 +0200, Jean Delvare wrote:
> If SIMPLE_DEV_PM_OPS causes it but UNIVERSAL_DEV_PM_OPS did not, I
> suppose that what matters is CONFIG_PM_SLEEP.
> 
> So maybe we can just replace "#ifdef CONFIG_PM" with "ifdef
> CONFIG_PM_SLEEP" in the code below?

It seems that drivers i2c-brcmstb, i2c-mpc, i2c-ocores, i2c-pnx,
i2c-puv3, i2c-st, i2c-stu300 and i2c-mux-pca954x are doing exactly that
already, so that must be a valid way to solve the problem.

Will you send a new patch?

Thanks,
-- 
Jean Delvare
SUSE L3 Support

[PATCH v2] i2c: i801: fix unused-function warning

[Anders Roxell]

With CONFIG_PM, we get a harmless build warning:
drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
 static int i801_resume(struct device *dev)
            ^~~~~~~~~~~
drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
 static int i801_suspend(struct device *dev)
            ^~~~~~~~~~~~

Follow design pattern from other drivers like i2c-brcmstb, i2c-mpc,
i2c-ocores, i2c-pnx, i2c-puv3, i2c-st, i2c-stu300 and i2c-mux-pca954x
and changing the ifdef CONFIG_PM to CONFIG_PM_SLEEP.

Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 drivers/i2c/busses/i2c-i801.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index ed07f9002710..954fb3f3b7fc 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1710,7 +1710,7 @@ static void i801_shutdown(struct pci_dev *dev)
 	pci_write_config_byte(dev, SMBHSTCFG, priv->original_hstcfg);
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int i801_suspend(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-- 
2.17.0

Re: [PATCH v2] i2c: i801: fix unused-function warning

[Jean Delvare]

On Mon, 14 May 2018 11:33:26 +0200, Anders Roxell wrote:
> With CONFIG_PM, we get a harmless build warning:
> drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
>  static int i801_resume(struct device *dev)
>             ^~~~~~~~~~~
> drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
>  static int i801_suspend(struct device *dev)
>             ^~~~~~~~~~~~
> 
> Follow design pattern from other drivers like i2c-brcmstb, i2c-mpc,
> i2c-ocores, i2c-pnx, i2c-puv3, i2c-st, i2c-stu300 and i2c-mux-pca954x
> and changing the ifdef CONFIG_PM to CONFIG_PM_SLEEP.
> 
> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
> ---
>  drivers/i2c/busses/i2c-i801.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index ed07f9002710..954fb3f3b7fc 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -1710,7 +1710,7 @@ static void i801_shutdown(struct pci_dev *dev)
>  	pci_write_config_byte(dev, SMBHSTCFG, priv->original_hstcfg);
>  }
>  
> -#ifdef CONFIG_PM
> +#ifdef CONFIG_PM_SLEEP
>  static int i801_suspend(struct device *dev)
>  {
>  	struct pci_dev *pci_dev = to_pci_dev(dev);

Reviewed-by: Jean Delvare <jdelvare@suse.de>

Thanks,
-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH v2] i2c: i801: fix unused-function warning

[Andy Shevchenko]

On Mon, May 14, 2018 at 12:33 PM, Anders Roxell
<anders.roxell@linaro.org> wrote:
> With CONFIG_PM, we get a harmless build warning:
> drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
>  static int i801_resume(struct device *dev)
>             ^~~~~~~~~~~
> drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
>  static int i801_suspend(struct device *dev)
>             ^~~~~~~~~~~~

> -#ifdef CONFIG_PM
> +#ifdef CONFIG_PM_SLEEP
>  static int i801_suspend(struct device *dev)

The better pattern is to get rid of ugly ifdef and supply
__maybe_unused annotation to each function in question.


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] i2c: i801: fix unused-function warning

[Jean Delvare]

Hi Andy,

On Mon, 14 May 2018 20:18:37 +0300, Andy Shevchenko wrote:
> On Mon, May 14, 2018 at 12:33 PM, Anders Roxell
> <anders.roxell@linaro.org> wrote:
> > With CONFIG_PM, we get a harmless build warning:
> > drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
> >  static int i801_resume(struct device *dev)
> >             ^~~~~~~~~~~
> > drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
> >  static int i801_suspend(struct device *dev)
> >             ^~~~~~~~~~~~  
> 
> > -#ifdef CONFIG_PM
> > +#ifdef CONFIG_PM_SLEEP
> >  static int i801_suspend(struct device *dev)  
> 
> The better pattern is to get rid of ugly ifdef and supply
> __maybe_unused annotation to each function in question.

That was Anders' first proposal, but it was declined by the driver
maintainer (me.) See:

https://marc.info/?l=linux-kernel&m=152588526520326&w=2

__maybe_unused is just a way to prevent the compiler from doing its
job. If it's really what you want, you might as well build with
-Wno-unused, instead of crippling the code with yet another annotation.

I can't see how building unused code only to discard it later can be
better than a proper #ifdef which will only build the code when we
actually need it.

Maybe there are cases where __maybe_unused is actually needed, but in
my opinion that should be the last resort option. That's not the case
here.

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH v2] i2c: i801: fix unused-function warning

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 871 bytes --]

On Mon, May 14, 2018 at 11:33:26AM +0200, Anders Roxell wrote:
> With CONFIG_PM, we get a harmless build warning:
> drivers/i2c/busses/i2c-i801.c:1723:12: warning: ‘i801_resume’ defined but not used [-Wunused-function]
>  static int i801_resume(struct device *dev)
>             ^~~~~~~~~~~
> drivers/i2c/busses/i2c-i801.c:1714:12: warning: ‘i801_suspend’ defined but not used [-Wunused-function]
>  static int i801_suspend(struct device *dev)
>             ^~~~~~~~~~~~
> 
> Follow design pattern from other drivers like i2c-brcmstb, i2c-mpc,
> i2c-ocores, i2c-pnx, i2c-puv3, i2c-st, i2c-stu300 and i2c-mux-pca954x
> and changing the ifdef CONFIG_PM to CONFIG_PM_SLEEP.
> 
> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

Applied to for-next, thanks!


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[PATCH] i2c: i801: mark PM functions as __maybe_unused

[Arnd Bergmann]

Changing from UNIVERSAL_DEV_PM_OPS to SIMPLE_DEV_PM_OPS caused a harmless
warning in configurations without CONFIG_PM_SLEEP:

drivers/i2c/busses/i2c-i801.c:1723:12: error: 'i801_resume' defined but not used [-Werror=unused-function]
 static int i801_resume(struct device *dev)
            ^~~~~~~~~~~
drivers/i2c/busses/i2c-i801.c:1714:12: error: 'i801_suspend' defined but not used [-Werror=unused-function]
 static int i801_suspend(struct device *dev)

This removes the incorrect #ifdef and instead marks both functions as
__maybe_unused, which is a more robust way to express the same thing.

Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/i2c/busses/i2c-i801.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index ed07f9002710..d6d46e7a5376 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1710,8 +1710,7 @@ static void i801_shutdown(struct pci_dev *dev)
 	pci_write_config_byte(dev, SMBHSTCFG, priv->original_hstcfg);
 }
 
-#ifdef CONFIG_PM
-static int i801_suspend(struct device *dev)
+static int __maybe_unused i801_suspend(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct i801_priv *priv = pci_get_drvdata(pci_dev);
@@ -1720,7 +1719,7 @@ static int i801_suspend(struct device *dev)
 	return 0;
 }
 
-static int i801_resume(struct device *dev)
+static int __maybe_unused i801_resume(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct i801_priv *priv = pci_get_drvdata(pci_dev);
@@ -1729,7 +1728,6 @@ static int i801_resume(struct device *dev)
 
 	return 0;
 }
-#endif
 
 static SIMPLE_DEV_PM_OPS(i801_pm_ops, i801_suspend, i801_resume);
 
-- 
2.9.0

Re: [PATCH] i2c: i801: mark PM functions as __maybe_unused

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 1032 bytes --]

On Fri, May 25, 2018 at 11:09:46PM +0200, Arnd Bergmann wrote:
> Changing from UNIVERSAL_DEV_PM_OPS to SIMPLE_DEV_PM_OPS caused a harmless
> warning in configurations without CONFIG_PM_SLEEP:
> 
> drivers/i2c/busses/i2c-i801.c:1723:12: error: 'i801_resume' defined but not used [-Werror=unused-function]
>  static int i801_resume(struct device *dev)
>             ^~~~~~~~~~~
> drivers/i2c/busses/i2c-i801.c:1714:12: error: 'i801_suspend' defined but not used [-Werror=unused-function]
>  static int i801_suspend(struct device *dev)
> 
> This removes the incorrect #ifdef and instead marks both functions as
> __maybe_unused, which is a more robust way to express the same thing.
> 
> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Should be fixed in my for-next branch:

https://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git/commit/drivers/i2c/busses/i2c-i801.c?h=i2c/for-next&id=4b2f9bd5e39fb47011074c9a26b64b616acc18f0


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