linux-kernel - [PATCH v2 6/9] PM: runtime: Introduce __rpm_get_driver

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Message-ID: <3909078.kQq0lBPeGt@rjwysocki.net>
Date: Thu, 26 Jun 2025 20:06:27 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Linux ACPI <linux-acpi@...r.kernel.org>,
 Linux PCI <linux-pci@...r.kernel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH v2 6/9] PM: runtime: Introduce __rpm_get_driver_callback()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Add a special function for computing the address of the runtime PM
callback given by an offset relative to the start of the device
driver's struct dev_pm_ops and use it to obtain the driver callback
in __rpm_get_callback().

Also put the shared part of the callback address computation into a
separate helper function to avoid code duplication and explicit
pointer type casts.

The new __rpm_get_driver_callback() will be used subsequently for
implementing callback lookup in pm_runtime_force_suspend/resume().

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v1 -> v2: New patch (not actually posted in v1 by mistake)

---
 drivers/base/power/runtime.c |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -19,10 +19,24 @@

 typedef int (*pm_callback_t)(struct device *);

+static inline pm_callback_t get_callback_ptr(const void *start, size_t offset)
+{
+	return *(pm_callback_t *)(start + offset);
+}
+
+static pm_callback_t __rpm_get_driver_callback(struct device *dev,
+					       size_t cb_offset)
+{
+	if (dev->driver && dev->driver->pm)
+		return get_callback_ptr(dev->driver->pm, cb_offset);
+
+	return NULL;
+}
+
 static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
 {
-	pm_callback_t cb;
 	const struct dev_pm_ops *ops;
+	pm_callback_t cb = NULL;

 	if (dev->pm_domain)
 		ops = &dev->pm_domain->ops;
@@ -36,12 +50,10 @@
 		ops = NULL;

 	if (ops)
-		cb = *(pm_callback_t *)((void *)ops + cb_offset);
-	else
-		cb = NULL;
+		cb = get_callback_ptr(ops, cb_offset);

-	if (!cb && dev->driver && dev->driver->pm)
-		cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
+	if (!cb)
+		cb = __rpm_get_driver_callback(dev, cb_offset);

 	return cb;
 }