[PATCH 1/8] driver core: Add helper for accessing Power Management callbacs

[Krzysztof Wilczyński <kw@xxxxxxxxx>]

Add driver_to_pm() helper allowing for accessing the Power Management
callbacs for a particular device.  Access to the callbacs (struct
dev_pm_ops) is normally done through using the pm pointer that is
embedded within the device_driver struct.

Helper allows for the code required to reference the pm pointer and
access Power Management callbas to be simplified.  Changing the
following:

  struct device_driver *drv = dev->driver;
  if (dev->driver && dev->driver->pm && dev->driver->pm->prepare) {
      int ret = dev->driver->pm->prepare(dev);

To:

  const struct dev_pm_ops *pm = driver_to_pm(dev->driver);
  if (pm && pm->prepare) {
      int ret = pm->prepare(dev);

Or, changing the following:

     const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

To:
     const struct dev_pm_ops *pm = driver_to_pm(dev->driver);

Signed-off-by: Krzysztof Wilczyński <kw@xxxxxxxxx>
---
 include/linux/device/driver.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h
index ee7ba5b5417e..ccd0b315fd93 100644
--- a/include/linux/device/driver.h
+++ b/include/linux/device/driver.h
@@ -236,6 +236,21 @@ driver_find_device_by_acpi_dev(struct device_driver *drv, const void *adev)
 }
 #endif
 
+/**
+ * driver_to_pm - Return Power Management callbacs (struct dev_pm_ops) for
+ *                a particular device.
+ * @drv: Pointer to a device (struct device_driver) for which you want to access
+ *       the Power Management callbacks.
+ *
+ * Returns a pointer to the struct dev_pm_ops embedded within the device (struct
+ * device_driver), or returns NULL if Power Management is not present and the
+ * pointer is not valid.
+ */
+static inline const struct dev_pm_ops *driver_to_pm(struct device_driver *drv)
+{
+	return drv && drv->pm ? drv->pm : NULL;
+}
+
 extern int driver_deferred_probe_timeout;
 void driver_deferred_probe_add(struct device *dev);
 int driver_deferred_probe_check_state(struct device *dev);
-- 
2.26.2