Re: [PATCH V2 4/4] pinctrl: add one more "const" for generic function groups

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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On Tue, Jan 11, 2022 at 05:51:44PM +0100, Rafał Miłecki wrote:
> On 11.01.2022 16:34, Nathan Chancellor wrote:
> > On Thu, Dec 16, 2021 at 05:22:06PM +0100, Rafał Miłecki wrote:
> > > From: Rafał Miłecki <rafal@milecki.pl>
> > > 
> > > Generic code doesn't modify those strings and .get_function_groups
> > > callback has that extra "const" as well. This allows more flexibility in
> > > GENERIC_PINMUX_FUNCTIONS users.
> > > 
> > > Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
> > > ---
> > >   drivers/pinctrl/pinmux.c | 2 +-
> > >   drivers/pinctrl/pinmux.h | 4 ++--
> > >   2 files changed, 3 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
> > > index 6cdbd9ccf2f0..f94d43b082d9 100644
> > > --- a/drivers/pinctrl/pinmux.c
> > > +++ b/drivers/pinctrl/pinmux.c
> > > @@ -875,7 +875,7 @@ EXPORT_SYMBOL_GPL(pinmux_generic_get_function);
> > >    */
> > >   int pinmux_generic_add_function(struct pinctrl_dev *pctldev,
> > >   				const char *name,
> > > -				const char **groups,
> > > +				const char * const *groups,
> > >   				const unsigned int num_groups,
> > >   				void *data)
> > >   {
> > > diff --git a/drivers/pinctrl/pinmux.h b/drivers/pinctrl/pinmux.h
> > > index 78c3a31be882..72fcf03eaa43 100644
> > > --- a/drivers/pinctrl/pinmux.h
> > > +++ b/drivers/pinctrl/pinmux.h
> > > @@ -129,7 +129,7 @@ static inline void pinmux_init_device_debugfs(struct dentry *devroot,
> > >    */
> > >   struct function_desc {
> > >   	const char *name;
> > > -	const char **group_names;
> > > +	const char * const *group_names;
> > >   	int num_group_names;
> > >   	void *data;
> > >   };
> > > @@ -150,7 +150,7 @@ struct function_desc *pinmux_generic_get_function(struct pinctrl_dev *pctldev,
> > >   int pinmux_generic_add_function(struct pinctrl_dev *pctldev,
> > >   				const char *name,
> > > -				const char **groups,
> > > +				const char * const *groups,
> > >   				unsigned const num_groups,
> > >   				void *data);
> > > -- 
> > > 2.31.1
> > > 
> > > 
> > 
> > I have not seen this reported yet, even though it has been broken for a
> > couple of weeks now. I see the following error in -next:
> > 
> > $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- allmodconfig drivers/pinctrl/pinctrl-thunderbay.o
> > drivers/pinctrl/pinctrl-thunderbay.c: In function ‘thunderbay_add_functions’:
> > drivers/pinctrl/pinctrl-thunderbay.c:815:29: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
> >    815 |                         grp = func->group_names;
> >        |                             ^
> > cc1: all warnings being treated as errors
> > 
> > Looks like something like the third patch of the series is needed for
> > the Thunderbay driver, which it appears was in development at the same
> > time as this series.
> 
> Correct, this driver didn't exist in Linus's tree when I developed my changes.

I stumbled above this issue, too. For the record, this patch fixes the
build issue:

diff --git a/drivers/pinctrl/pinctrl-thunderbay.c b/drivers/pinctrl/pinctrl-thunderbay.c
index b5b47f4dd774..a6a9a0cca6bf 100644
--- a/drivers/pinctrl/pinctrl-thunderbay.c
+++ b/drivers/pinctrl/pinctrl-thunderbay.c
@@ -812,7 +812,7 @@ static int thunderbay_add_functions(struct thunderbay_pinctrl *tpc, struct funct
 				}
 			}
 
-			grp = func->group_names;
+			grp = (void *)func->group_names;
 			while (*grp)
 				grp++;
 
(however it's probably not safe for runtime).

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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