Re: [PATCH] platform/x86: dell-wmi-sysman: Use sysfs_emit{_at} in show functions

[Ilpo Järvinen]

On Thu, 5 Mar 2026, Thorsten Blum wrote:

> Replace sprintf() with sysfs_emit() and sysfs_emit_at() in sysfs show
> functions. sysfs_emit() and sysfs_emit_at() are preferred for formatting
> sysfs output because they provide safer bounds checking.
> 
> In reset_bios_show(), use sysfs_emit_at() to avoid manual buffer size
> accounting.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxx>
> ---
>  .../platform/x86/dell/dell-wmi-sysman/sysman.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
> index 9dddab6c9397..0f24cecc93fc 100644
> --- a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
> +++ b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
> @@ -11,6 +11,7 @@
>  #include <linux/dmi.h>
>  #include <linux/module.h>
>  #include <linux/kernel.h>
> +#include <linux/sysfs.h>
>  #include <linux/wmi.h>
>  #include "dell-wmi-sysman.h"
>  #include "../../firmware_attributes_class.h"
> @@ -143,17 +144,14 @@ int map_wmi_error(int error_code)
>   */
>  static ssize_t reset_bios_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
>  {
> -	char *start = buf;
> +	ssize_t len = 0;
>  	int i;
>  
> -	for (i = 0; i < MAX_TYPES; i++) {
> -		if (i == reset_option)
> -			buf += sprintf(buf, "[%s] ", reset_types[i]);
> -		else
> -			buf += sprintf(buf, "%s ", reset_types[i]);
> -	}
> -	buf += sprintf(buf, "\n");
> -	return buf-start;
> +	for (i = 0; i < MAX_TYPES; i++)
> +		len += sysfs_emit_at(buf, len, i == reset_option ? "[%s] " : "%s ",

Are all checkers okay with this construct? IIRC something doesn't 
like having such logic in where only a formatting string is expected.

--
 i.

> +				     reset_types[i]);
> +	len += sysfs_emit_at(buf, len, "\n");
> +	return len;
>  }
>  
>  /**
> @@ -194,7 +192,7 @@ static ssize_t reset_bios_store(struct kobject *kobj,
>  static ssize_t pending_reboot_show(struct kobject *kobj, struct kobj_attribute *attr,
>  				   char *buf)
>  {
> -	return sprintf(buf, "%d\n", wmi_priv.pending_changes);
> +	return sysfs_emit(buf, "%d\n", wmi_priv.pending_changes);
>  }
>  
>  static struct kobj_attribute reset_bios = __ATTR_RW(reset_bios);
>