linux-kernel - [PATCH v2 2/3] PM: runtime: Allow unassigned ->runtime

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Date:   Tue,  8 Jun 2021 11:02:49 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] PM: runtime: Allow unassigned ->runtime_suspend|resume callbacks

We are currently allowing ->runtime_idle() callbacks to be unassigned
without returning an error code from rpm_idle(). This has been useful to
avoid boilerplate code in drivers. Let's take this approach a step further,
by allowing also unassigned ->runtime_suspend|resume() callbacks.

In this way, a consumer/supplier device link can be used to let a consumer
device be power managed through its supplier device, without requiring
assigned ->runtime_suspend|resume() callbacks for the consumer device, for
example.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---

Changes in v2:
	- Small updates to commit message.

---
 drivers/base/power/runtime.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 68bebbf81347..8a66eaf731e4 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -345,7 +345,7 @@ static void rpm_suspend_suppliers(struct device *dev)
 static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
 	__releases(&dev->power.lock) __acquires(&dev->power.lock)
 {
-	int retval, idx;
+	int retval = 0, idx;
 	bool use_links = dev->power.links_count > 0;
 
 	if (dev->power.irq_safe) {
@@ -373,7 +373,8 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
 		}
 	}
 
-	retval = cb(dev);
+	if (cb)
+		retval = cb(dev);
 
 	if (dev->power.irq_safe) {
 		spin_lock(&dev->power.lock);
@@ -484,9 +485,6 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
 {
 	int retval;
 
-	if (!cb)
-		return -ENOSYS;
-
 	if (dev->power.memalloc_noio) {
 		unsigned int noio_flag;
 
-- 
2.25.1