Re: [PATCH v2] cpuidle: sysfs: Use sysfs_emit/sysfs_emit_at instead of sprintf/scnprintf

[Rafael J. Wysocki]

On Fri, Sep 19, 2025 at 6:57 PM <vivekyadav1207731111@xxxxxxxxx> wrote:
>
> From: Vivek Yadav <vivekyadav1207731111@xxxxxxxxx>
>
> The ->show() callbacks in sysfs should use sysfs_emit() or
> sysfs_emit_at() when formatting values for user space. These helpers
> are the recommended way to ensure correct buffer handling and
> consistency across the kernel.
>
> See Documentation/filesystems/sysfs.rst for details.
>
> No functional change intended.
>
> Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
> Signed-off-by: Vivek Yadav <vivekyadav1207731111@xxxxxxxxx>
> ---
>  drivers/cpuidle/sysfs.c | 34 +++++++++++++++++-----------------
>  1 file changed, 17 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
> index d6f5da61cb7d..61de64817604 100644
> --- a/drivers/cpuidle/sysfs.c
> +++ b/drivers/cpuidle/sysfs.c
> @@ -27,14 +27,14 @@ static ssize_t show_available_governors(struct device *dev,
>
>         mutex_lock(&cpuidle_lock);
>         list_for_each_entry(tmp, &cpuidle_governors, governor_list) {
> -               if (i >= (ssize_t) (PAGE_SIZE - (CPUIDLE_NAME_LEN + 2)))
> +               if (i >= (ssize_t)(PAGE_SIZE - (CPUIDLE_NAME_LEN + 2)))
>                         goto out;
>
> -               i += scnprintf(&buf[i], CPUIDLE_NAME_LEN + 1, "%s ", tmp->name);
> +               i += sysfs_emit_at(buf, i, "%.*s ", CPUIDLE_NAME_LEN, tmp->name);
>         }
>
>  out:
> -       i+= sprintf(&buf[i], "\n");
> +       i += sysfs_emit_at(buf, i, "\n");
>         mutex_unlock(&cpuidle_lock);
>         return i;
>  }
> @@ -49,9 +49,9 @@ static ssize_t show_current_driver(struct device *dev,
>         spin_lock(&cpuidle_driver_lock);
>         drv = cpuidle_get_driver();
>         if (drv)
> -               ret = sprintf(buf, "%s\n", drv->name);
> +               ret = sysfs_emit(buf, "%s\n", drv->name);
>         else
> -               ret = sprintf(buf, "none\n");
> +               ret = sysfs_emit(buf, "none\n");
>         spin_unlock(&cpuidle_driver_lock);
>
>         return ret;
> @@ -65,9 +65,9 @@ static ssize_t show_current_governor(struct device *dev,
>
>         mutex_lock(&cpuidle_lock);
>         if (cpuidle_curr_governor)
> -               ret = sprintf(buf, "%s\n", cpuidle_curr_governor->name);
> +               ret = sysfs_emit(buf, "%s\n", cpuidle_curr_governor->name);
>         else
> -               ret = sprintf(buf, "none\n");
> +               ret = sysfs_emit(buf, "none\n");
>         mutex_unlock(&cpuidle_lock);
>
>         return ret;
> @@ -230,7 +230,7 @@ static struct cpuidle_state_attr attr_##_name = __ATTR(_name, 0644, show, store)
>  static ssize_t show_state_##_name(struct cpuidle_state *state, \
>                          struct cpuidle_state_usage *state_usage, char *buf) \
>  { \
> -       return sprintf(buf, "%u\n", state->_name);\
> +       return sysfs_emit(buf, "%u\n", state->_name);\
>  }
>
>  #define define_show_state_ull_function(_name) \
> @@ -238,7 +238,7 @@ static ssize_t show_state_##_name(struct cpuidle_state *state, \
>                                   struct cpuidle_state_usage *state_usage, \
>                                   char *buf)                            \
>  { \
> -       return sprintf(buf, "%llu\n", state_usage->_name);\
> +       return sysfs_emit(buf, "%llu\n", state_usage->_name);\
>  }
>
>  #define define_show_state_str_function(_name) \
> @@ -247,8 +247,8 @@ static ssize_t show_state_##_name(struct cpuidle_state *state, \
>                                   char *buf)                            \
>  { \
>         if (state->_name[0] == '\0')\
> -               return sprintf(buf, "<null>\n");\
> -       return sprintf(buf, "%s\n", state->_name);\
> +               return sysfs_emit(buf, "<null>\n");\
> +       return sysfs_emit(buf, "%s\n", state->_name);\
>  }
>
>  #define define_show_state_time_function(_name) \
> @@ -256,7 +256,7 @@ static ssize_t show_state_##_name(struct cpuidle_state *state, \
>                                   struct cpuidle_state_usage *state_usage, \
>                                   char *buf) \
>  { \
> -       return sprintf(buf, "%llu\n", ktime_to_us(state->_name##_ns)); \
> +       return sysfs_emit(buf, "%llu\n", ktime_to_us(state->_name##_ns)); \
>  }
>
>  define_show_state_time_function(exit_latency)
> @@ -273,14 +273,14 @@ static ssize_t show_state_time(struct cpuidle_state *state,
>                                struct cpuidle_state_usage *state_usage,
>                                char *buf)
>  {
> -       return sprintf(buf, "%llu\n", ktime_to_us(state_usage->time_ns));
> +       return sysfs_emit(buf, "%llu\n", ktime_to_us(state_usage->time_ns));
>  }
>
>  static ssize_t show_state_disable(struct cpuidle_state *state,
>                                   struct cpuidle_state_usage *state_usage,
>                                   char *buf)
>  {
> -       return sprintf(buf, "%llu\n",
> +       return sysfs_emit(buf, "%llu\n",
>                        state_usage->disable & CPUIDLE_STATE_DISABLED_BY_USER);
>  }
>
> @@ -310,7 +310,7 @@ static ssize_t show_state_default_status(struct cpuidle_state *state,
>                                           struct cpuidle_state_usage *state_usage,
>                                           char *buf)
>  {
> -       return sprintf(buf, "%s\n",
> +       return sysfs_emit(buf, "%s\n",
>                        state->flags & CPUIDLE_FLAG_OFF ? "disabled" : "enabled");
>  }
>
> @@ -358,7 +358,7 @@ static ssize_t show_state_s2idle_##_name(struct cpuidle_state *state, \
>                                          struct cpuidle_state_usage *state_usage, \
>                                          char *buf)                             \
>  { \
> -       return sprintf(buf, "%llu\n", state_usage->s2idle_##_name);\
> +       return sysfs_emit(buf, "%llu\n", state_usage->s2idle_##_name);\
>  }
>
>  define_show_state_s2idle_ull_function(usage);
> @@ -550,7 +550,7 @@ static ssize_t show_driver_name(struct cpuidle_driver *drv, char *buf)
>         ssize_t ret;
>
>         spin_lock(&cpuidle_driver_lock);
> -       ret = sprintf(buf, "%s\n", drv ? drv->name : "none");
> +       ret = sysfs_emit(buf, "%s\n", drv ? drv->name : "none");
>         spin_unlock(&cpuidle_driver_lock);
>
>         return ret;
> --

Applied as 6.18 material, thanks!