linux-kernel - Re: [PATCH v1 23/23] PM: runtime: Change pm_runtime

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Message-ID: <aVwtuIfYH6CgQDP_@google.com>
Date: Mon, 5 Jan 2026 13:31:36 -0800
From: Brian Norris <briannorris@...omium.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v1 23/23] PM: runtime: Change pm_runtime_put() return
 type to void

On Mon, Dec 22, 2025 at 09:36:25PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The primary role of pm_runtime_put() is to decrement the runtime PM
> usage counter of the given device.  It always does that regardless of
> the value returned by it later.
> 
> In addition, if the runtime PM usage counter after decrementation turns
> out to be zero, a work item is queued up to check whether or not the
> device can be suspended.  This is not guaranteed to succeed though and
> even if it is successful, the device may still not be suspended going
> forward.
> 
> There are multiple valid reasons why pm_runtime_put() may not decide to
> queue up the work item mentioned above, including, but not limited to,
> the case when user space has written "on" to the device's runtime PM
> "control" file in sysfs.  In all of those cases, pm_runtime_put()
> returns a negative error code (even though the device's runtime PM
> usage counter has been successfully decremented by it) which is very
> confusing.  In fact, its return value should only be used for debug
> purposes and care should be taken when doing it even in that case.
> 
> Accordingly, to avoid the confusion mentioned above, change the return
> type of pm_runtime_put() to void.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  include/linux/pm_runtime.h |   16 ++--------------
>  1 file changed, 2 insertions(+), 14 deletions(-)

I'm always happy to see rough edges of the runtime PM API sanded off.
Thanks for doing this!

Reviewed-by: Brian Norris <briannorris@...omium.org>