Re: [PATCH v1 2/2] PM: Add config flag to gate sysfs wakeup_sources

Rafael J. Wysocki
2026-03-20T16:09:25Z

On Fri, Mar 20, 2026 at 5:01 PM Samuel Wu <wusamuel@google.com> wrote:
>
> Add a config flag that gates the creation of
> /sys/class/wakeup_sources/*. This has the benefit of eliminating the
> work needed to create the nodes and corresponding attributes; and
> between kernfs, dentry, and malloc, there are some memory savings
> depending on the number of wakeup sources.
>
> Signed-off-by: Samuel Wu <wusamuel@google.com>
> ---
> drivers/base/power/Makefile | 3 ++-
> drivers/base/power/power.h | 14 ++++++++++++++
> kernel/power/Kconfig | 13 +++++++++++++
> 3 files changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
> index 2989e42d0161..5933dadc0dd9 100644
> --- a/drivers/base/power/Makefile
> +++ b/drivers/base/power/Makefile
> @@ -1,6 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0
> obj-$(CONFIG_PM) += sysfs.o generic_ops.o common.o qos.o runtime.o wakeirq.o
> -obj-$(CONFIG_PM_SLEEP) += main.o wakeup.o wakeup_stats.o
> +obj-$(CONFIG_PM_SLEEP) += main.o wakeup.o
> +obj-$(CONFIG_PM_WAKEUP_STATS_SYSFS) += wakeup_stats.o
> obj-$(CONFIG_PM_TRACE_RTC) += trace.o
> obj-$(CONFIG_HAVE_CLK) += clock_ops.o
> obj-$(CONFIG_PM_QOS_KUNIT_TEST) += qos-test.o
> diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
> index 922ed457db19..364ca5512b4f 100644
> --- a/drivers/base/power/power.h
> +++ b/drivers/base/power/power.h
> @@ -125,11 +125,25 @@ static inline bool device_pm_initialized(struct device *dev)
> }
>
> /* drivers/base/power/wakeup_stats.c */
> +#ifdef CONFIG_PM_WAKEUP_STATS_SYSFS
> extern int wakeup_source_sysfs_add(struct device *parent,
> struct wakeup_source *ws);
> extern void wakeup_source_sysfs_remove(struct wakeup_source *ws);
>
> extern int pm_wakeup_source_sysfs_add(struct device *parent);
> +#else /* !CONFIG_PM_WAKEUP_STATS_SYSFS */
> +static inline int wakeup_source_sysfs_add(struct device *parent,
> + struct wakeup_source *ws)
> +{
> + return 0;
> +}
> +static inline void wakeup_source_sysfs_remove(struct wakeup_source *ws) {}
> +
> +static inline int pm_wakeup_source_sysfs_add(struct device *parent)
> +{
> + return 0;
> +}
> +#endif /* !CONFIG_PM_WAKEUP_STATS_SYSFS */
>
> #else /* !CONFIG_PM_SLEEP */
>
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 05337f437cca..6945083ab053 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -202,6 +202,19 @@ config PM_WAKELOCKS_GC
> depends on PM_WAKELOCKS
> default y
>
> +config PM_WAKEUP_STATS_SYSFS
> + bool "Sysfs wakeup statistics"
> + depends on PM_SLEEP
> + default y
> + help
> + Enable this for wakeup statistics in sysfs under /sys/class/wakeup/
> +
> + Disabling this option eliminates the work of creating the wakeup
> + sources and each of their attributes in sysfs. Depending on the
> + number of wakeup sources, this can also have a non-negligible memory
> + impact. Regardless of this config option's value, wakeup statistics
> + are still available via debugfs and BPF.

Well, except that otherwise it may be hard to figure out which device
the given wakeup source belongs to, so I'd rather not do that.

> +
> config PM_QOS_CPU_SYSTEM_WAKEUP
> bool "User space interface for CPU system wakeup QoS"
> depends on CPU_IDLE
> --