Re: [PATCH 07/15] PM QoS: add a global notification mechanism for the device constraints

From: Jean Pihet <redacted>

Add a global notification chain that gets called upon changes to the
aggregated constraint value for any device.
The notification callbacks are passing the full constraint request data
in order for the callees to have access to it. The current use is for the
platform low-level code to access the target device of the constraint.

Signed-off-by: Jean Pihet <redacted>
---
 drivers/base/power/qos.c |   84 ++++++++++++++++++++++++++++++++++++----------
 include/linux/pm_qos.h   |   11 ++++++
 kernel/power/qos.c       |    2 +-
 3 files changed, 78 insertions(+), 19 deletions(-)

diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index 304d68d..b52b3e8 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c

@@ -8,6 +8,12 @@
  *
  * This QoS design is best effort based. Dependents register their QoS needs.
  * Watchers register to keep track of the current QoS needs of the system.
+ * Watchers can register different types of notification callbacks:
+ *  . a per-device notification callback using the dev_pm_qos_*_notifier API.
+ *    The notification chain data is stored in the per-device constraint
+ *    data struct.
+ *  . a system-wide notification callback using the dev_pm_qos_*_global_notifier
+ *    API. The notification chain data is stored in a static variable.
  *
  * Note about the per-device constraint data struct allocation:
  * . The per-device constraints data struct ptr is tored into the device

@@ -36,8 +42,32 @@
 
 
 static DEFINE_MUTEX(dev_pm_qos_mtx);
+static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);
 static void dev_pm_qos_constraints_allocate(struct device *dev);
 
+/*
+ * Update the constraints list using the PM QoS core code and
+ * if needed call the per-device and the global notification callbacks
+ */