Re: [PATCH v2 2/2] PM: Use sysfs_emit() and sysfs_emit_at() in "show" functions

From: Rafael J. Wysocki
Date: Wed Jul 31 2024 - 06:55:43 EST

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In reply to: xueqin Luo: "[PATCH v2 2/2] PM: Use sysfs_emit() and sysfs_emit_at() in "show" functions"
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On Wed, Jul 31, 2024 at 4:45 AM xueqin Luo <luoxueqin@xxxxxxxxxx> wrote:
>
> From: Xueqin Luo <luoxueqin@xxxxxxxxxx>
>
> As Documentation/filesystems/sysfs.rst suggested,
> show() should only use sysfs_emit() or sysfs_emit_at() when formatting
> the value to be returned to user space.
>
> No functional change intended.
>
> Signed-off-by: Xueqin Luo <luoxueqin@xxxxxxxxxx>
> ---
> kernel/power/main.c | 82 +++++++++++++++++++++++++--------------------
> 1 file changed, 45 insertions(+), 37 deletions(-)
>
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index a9e0693aaf69..18948b694205 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -115,7 +115,7 @@ int pm_async_enabled = 1;
> static ssize_t pm_async_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> - return sprintf(buf, "%d\n", pm_async_enabled);
> + return sysfs_emit(buf, "%d\n", pm_async_enabled);
> }
>
> static ssize_t pm_async_store(struct kobject *kobj, struct kobj_attribute *attr,
> @@ -139,8 +139,8 @@ power_attr(pm_async);
> static ssize_t mem_sleep_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> - char *s = buf;
> suspend_state_t i;
> + ssize_t sz = 0;

Please call the new variable "count", and analogously below and in the
first patch.

>
> for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++) {
> if (i >= PM_SUSPEND_MEM && cxl_mem_active())
> @@ -149,17 +149,19 @@ static ssize_t mem_sleep_show(struct kobject *kobj, struct kobj_attribute *attr,
> const char *label = mem_sleep_states[i];
>
> if (mem_sleep_current == i)
> - s += sprintf(s, "[%s] ", label);
> + sz += sysfs_emit_at(buf, sz, "[%s] ", label);
> else
> - s += sprintf(s, "%s ", label);
> + sz += sysfs_emit_at(buf, sz, "%s ", label);
> }
> }
>
> /* Convert the last space to a newline if needed. */
> - if (s != buf)
> - *(s-1) = '\n';
> + if (sz) {
> + sz--;
> + sz += sysfs_emit_at(buf, sz, "\n");
> + }

Why do you need to update the count var above? Something like this
should work too AFAICS:

if (count > 0)
sysfs_emit_at(buf, count - 1, "\n");

Analogously below.

>
> - return (s - buf);
> + return sz;
> }
>
> static suspend_state_t decode_suspend_state(const char *buf, size_t n)
> @@ -220,7 +222,7 @@ bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC);
> static ssize_t sync_on_suspend_show(struct kobject *kobj,
> struct kobj_attribute *attr, char *buf)
> {
> - return sprintf(buf, "%d\n", sync_on_suspend_enabled);
> + return sysfs_emit(buf, "%d\n", sync_on_suspend_enabled);
> }
>
> static ssize_t sync_on_suspend_store(struct kobject *kobj,
> @@ -257,22 +259,24 @@ static const char * const pm_tests[__TEST_AFTER_LAST] = {
> static ssize_t pm_test_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> - char *s = buf;
> int level;
> + size_t sz = 0;

Reverse xmas tree order, please.

>
> for (level = TEST_FIRST; level <= TEST_MAX; level++)
> if (pm_tests[level]) {
> if (level == pm_test_level)
> - s += sprintf(s, "[%s] ", pm_tests[level]);
> + sz += sysfs_emit_at(buf, sz, "[%s] ", pm_tests[level]);
> else
> - s += sprintf(s, "%s ", pm_tests[level]);
> + sz += sysfs_emit_at(buf, sz, "%s ", pm_tests[level]);
> }
>
> - if (s != buf)
> - /* convert the last space to a newline */
> - *(s-1) = '\n';
> + /* Convert the last space to a newline if needed. */
> + if (sz) {
> + sz--;
> + sz += sysfs_emit_at(buf, sz, "\n");
> + }
>
> - return (s - buf);
> + return sz;
> }
>
> static ssize_t pm_test_store(struct kobject *kobj, struct kobj_attribute *attr,
> @@ -390,7 +394,7 @@ static const char * const suspend_step_names[] = {
> static ssize_t _name##_show(struct kobject *kobj, \
> struct kobj_attribute *attr, char *buf) \
> { \
> - return sprintf(buf, format_str, suspend_stats._name); \
> + return sysfs_emit(buf, format_str, suspend_stats._name);\
> } \
> static struct kobj_attribute _name = __ATTR_RO(_name)
>
> @@ -404,7 +408,7 @@ suspend_attr(max_hw_sleep, "%llu\n");
> static ssize_t _name##_show(struct kobject *kobj, \
> struct kobj_attribute *attr, char *buf) \
> { \
> - return sprintf(buf, "%u\n", \
> + return sysfs_emit(buf, "%u\n", \
> suspend_stats.step_failures[step-1]); \
> } \
> static struct kobj_attribute _name = __ATTR_RO(_name)
> @@ -428,7 +432,7 @@ static ssize_t last_failed_dev_show(struct kobject *kobj,
> index %= REC_FAILED_NUM;
> last_failed_dev = suspend_stats.failed_devs[index];
>
> - return sprintf(buf, "%s\n", last_failed_dev);
> + return sysfs_emit(buf, "%s\n", last_failed_dev);
> }
> static struct kobj_attribute last_failed_dev = __ATTR_RO(last_failed_dev);
>
> @@ -442,7 +446,7 @@ static ssize_t last_failed_errno_show(struct kobject *kobj,
> index %= REC_FAILED_NUM;
> last_failed_errno = suspend_stats.errno[index];
>
> - return sprintf(buf, "%d\n", last_failed_errno);
> + return sysfs_emit(buf, "%d\n", last_failed_errno);
> }
> static struct kobj_attribute last_failed_errno = __ATTR_RO(last_failed_errno);
>
> @@ -456,7 +460,7 @@ static ssize_t last_failed_step_show(struct kobject *kobj,
> index %= REC_FAILED_NUM;
> step = suspend_stats.failed_steps[index];
>
> - return sprintf(buf, "%s\n", suspend_step_names[step]);
> + return sysfs_emit(buf, "%s\n", suspend_step_names[step]);
> }
> static struct kobj_attribute last_failed_step = __ATTR_RO(last_failed_step);
>
> @@ -571,7 +575,7 @@ bool pm_print_times_enabled;
> static ssize_t pm_print_times_show(struct kobject *kobj,
> struct kobj_attribute *attr, char *buf)
> {
> - return sprintf(buf, "%d\n", pm_print_times_enabled);
> + return sysfs_emit(buf, "%d\n", pm_print_times_enabled);
> }
>
> static ssize_t pm_print_times_store(struct kobject *kobj,
> @@ -604,7 +608,7 @@ static ssize_t pm_wakeup_irq_show(struct kobject *kobj,
> if (!pm_wakeup_irq())
> return -ENODATA;
>
> - return sprintf(buf, "%u\n", pm_wakeup_irq());
> + return sysfs_emit(buf, "%u\n", pm_wakeup_irq());
> }
>
> power_attr_ro(pm_wakeup_irq);
> @@ -620,7 +624,7 @@ EXPORT_SYMBOL_GPL(pm_debug_messages_should_print);
> static ssize_t pm_debug_messages_show(struct kobject *kobj,
> struct kobj_attribute *attr, char *buf)
> {
> - return sprintf(buf, "%d\n", pm_debug_messages_on);
> + return sysfs_emit(buf, "%d\n", pm_debug_messages_on);
> }
>
> static ssize_t pm_debug_messages_store(struct kobject *kobj,
> @@ -668,21 +672,25 @@ struct kobject *power_kobj;
> static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> - char *s = buf;
> + ssize_t sz = 0;
> #ifdef CONFIG_SUSPEND
> suspend_state_t i;
>
> for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++)
> if (pm_states[i])
> - s += sprintf(s,"%s ", pm_states[i]);
> + sz += sysfs_emit_at(buf, sz, "%s ", pm_states[i]);
>
> #endif
> if (hibernation_available())
> - s += sprintf(s, "disk ");
> - if (s != buf)
> - /* convert the last space to a newline */
> - *(s-1) = '\n';
> - return (s - buf);
> + sz += sysfs_emit_at(buf, sz, "disk ");
> +
> + /* Convert the last space to a newline if needed. */
> + if (sz) {
> + sz--;
> + sz += sysfs_emit_at(buf, sz, "\n");
> + }
> +
> + return sz;
> }
>
> static suspend_state_t decode_state(const char *buf, size_t n)
> @@ -782,7 +790,7 @@ static ssize_t wakeup_count_show(struct kobject *kobj,
> unsigned int val;
>
> return pm_get_wakeup_count(&val, true) ?
> - sprintf(buf, "%u\n", val) : -EINTR;
> + sysfs_emit(buf, "%u\n", val) : -EINTR;
> }
>
> static ssize_t wakeup_count_store(struct kobject *kobj,
> @@ -824,17 +832,17 @@ static ssize_t autosleep_show(struct kobject *kobj,
> suspend_state_t state = pm_autosleep_state();
>
> if (state == PM_SUSPEND_ON)
> - return sprintf(buf, "off\n");
> + return sysfs_emit(buf, "off\n");
>
> #ifdef CONFIG_SUSPEND
> if (state < PM_SUSPEND_MAX)
> - return sprintf(buf, "%s\n", pm_states[state] ?
> + return sysfs_emit(buf, "%s\n", pm_states[state] ?
> pm_states[state] : "error");
> #endif
> #ifdef CONFIG_HIBERNATION
> - return sprintf(buf, "disk\n");
> + return sysfs_emit(buf, "disk\n");
> #else
> - return sprintf(buf, "error");
> + return sysfs_emit(buf, "error\n");
> #endif
> }
>
> @@ -903,7 +911,7 @@ int pm_trace_enabled;
> static ssize_t pm_trace_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> - return sprintf(buf, "%d\n", pm_trace_enabled);
> + return sysfs_emit(buf, "%d\n", pm_trace_enabled);
> }
>
> static ssize_t
> @@ -940,7 +948,7 @@ power_attr_ro(pm_trace_dev_match);
> static ssize_t pm_freeze_timeout_show(struct kobject *kobj,
> struct kobj_attribute *attr, char *buf)
> {
> - return sprintf(buf, "%u\n", freeze_timeout_msecs);
> + return sysfs_emit(buf, "%u\n", freeze_timeout_msecs);
> }
>
> static ssize_t pm_freeze_timeout_store(struct kobject *kobj,
> --

Next message: Peter Zijlstra: "Re: Are jump labels broken on 6.11-rc1?"
Previous message: Arnd Bergmann: "Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together"
In reply to: xueqin Luo: "[PATCH v2 2/2] PM: Use sysfs_emit() and sysfs_emit_at() in "show" functions"
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