Re: [PATCH 1/2] sysfs: attribute_group: allow registration of const bin_attribute

["Thomas Weißschuh" <linux@weissschuh.net>]

Hi Greg,

On 2024-11-15 17:42:48+0100, Thomas Weißschuh wrote:

> [..]

> diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
> index d713a6445a6267145a7014f308df3bb25b8c3287..0f2fcd244523f050c5286f19d4fe1846506f9214 100644
> --- a/include/linux/sysfs.h
> +++ b/include/linux/sysfs.h
> @@ -106,7 +106,10 @@ struct attribute_group {
>  					    const struct bin_attribute *,
>  					    int);
>  	struct attribute	**attrs;
> -	struct bin_attribute	**bin_attrs;
> +	union {
> +		struct bin_attribute		**bin_attrs;
> +		const struct bin_attribute	*const *bin_attrs_new;
> +	};

Unfortunately this triggers warnings in two drivers.
These incorrectly have a trailing NULL literal in their struct attribute
definition (full list at the end of the mail):

>> drivers/perf/arm-ni.c:248:63: warning: missing braces around initializer [-Wmissing-braces]
     248 | static const struct attribute_group arm_ni_other_attr_group = {
         |                                                               ^


vim +248 drivers/perf/arm-ni.c

4d5a7680f2b4d0 Robin Murphy 2024-09-04  247
4d5a7680f2b4d0 Robin Murphy 2024-09-04 @248  static const struct attribute_group arm_ni_other_attr_group = {
4d5a7680f2b4d0 Robin Murphy 2024-09-04  249  	.attrs = arm_ni_other_attrs,
4d5a7680f2b4d0 Robin Murphy 2024-09-04  250  	NULL
4d5a7680f2b4d0 Robin Murphy 2024-09-04  251  };
4d5a7680f2b4d0 Robin Murphy 2024-09-04  252

These trailing NULLs should first be removed.
How do you want to proceed?

Cocci script and results, only the first two results are relevant at
this moment.

	virtual patch

	@@
	identifier ag, pattrs;
	@@

	  struct attribute_group ag = {
	    .attrs = pattrs,
	-   NULL
	  };

diff -u -p a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c
--- a/drivers/s390/char/con3215.c
+++ b/drivers/s390/char/con3215.c
@@ -803,7 +803,6 @@ static struct attribute *con3215_drv_att

 static struct attribute_group con3215_drv_attr_group = {
 	.attrs = con3215_drv_attrs,
-	NULL,
 };

 static const struct attribute_group *con3215_drv_attr_groups[] = {
diff -u -p a/drivers/perf/arm-ni.c b/drivers/perf/arm-ni.c
--- a/drivers/perf/arm-ni.c
+++ b/drivers/perf/arm-ni.c
@@ -247,7 +247,6 @@ static struct attribute *arm_ni_other_at

 static const struct attribute_group arm_ni_other_attr_group = {
 	.attrs = arm_ni_other_attrs,
-	NULL
 };

 static const struct attribute_group *arm_ni_attr_groups[] = {
diff -u -p a/kernel/cpu.c b/kernel/cpu.c
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2866,7 +2866,6 @@ static struct attribute *cpuhp_cpu_attrs
 static const struct attribute_group cpuhp_cpu_attr_group = {
 	.attrs = cpuhp_cpu_attrs,
 	.name = "hotplug",
-	NULL
 };

 static ssize_t states_show(struct device *dev,
@@ -2898,7 +2897,6 @@ static struct attribute *cpuhp_cpu_root_
 static const struct attribute_group cpuhp_cpu_root_attr_group = {
 	.attrs = cpuhp_cpu_root_attrs,
 	.name = "hotplug",
-	NULL
 };

 #ifdef CONFIG_HOTPLUG_SMT
@@ -3020,7 +3018,6 @@ static struct attribute *cpuhp_smt_attrs
 static const struct attribute_group cpuhp_smt_attr_group = {
 	.attrs = cpuhp_smt_attrs,
 	.name = "smt",
-	NULL
 };

 static int __init cpu_smt_sysfs_init(void)