linux-kernel - [PATCH v2 2/2] cpuidle: Change :enter_dead() driver callback return type to void

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Message-ID: <2285569.iZASKD2KPV@rjwysocki.net>
Date: Fri, 15 Nov 2024 22:00:25 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>
Cc: LKML <linux-kernel@...r.kernel.org>, x86 Maintainers <x86@...nel.org>,
 Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
 Mario Limonciello <mario.limonciello@....com>,
 Linux ACPI <linux-acpi@...r.kernel.org>
Subject:
 [PATCH v2 2/2] cpuidle: Change :enter_dead() driver callback return type to
 void

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

After a previous change, cpuidle_play_dead(), which is the only caller
of idle state :enter_dead() callbacks, ignores their return values, so
they may as well be void.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v1 -> v2: New patch

Interestingly enough, the only user of :enter_dead() idle state callbacks
in the current mainline turns out to be ACPI idle.

---
 drivers/acpi/processor_idle.c |    7 ++-----
 include/linux/cpuidle.h       |    2 +-
 2 files changed, 3 insertions(+), 6 deletions(-)

Index: linux-pm/include/linux/cpuidle.h
===================================================================
--- linux-pm.orig/include/linux/cpuidle.h
+++ linux-pm/include/linux/cpuidle.h
@@ -61,7 +61,7 @@ struct cpuidle_state {
 			struct cpuidle_driver *drv,
 			int index);

-	int (*enter_dead) (struct cpuidle_device *dev, int index);
+	void (*enter_dead) (struct cpuidle_device *dev, int index);

 	/*
 	 * CPUs execute ->enter_s2idle with the local tick or entire timekeeping
Index: linux-pm/drivers/acpi/processor_idle.c
===================================================================
--- linux-pm.orig/drivers/acpi/processor_idle.c
+++ linux-pm/drivers/acpi/processor_idle.c
@@ -578,7 +578,7 @@ static void __cpuidle acpi_idle_do_entry
  * @dev: the target CPU
  * @index: the index of suggested state
  */
-static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
+static void acpi_idle_play_dead(struct cpuidle_device *dev, int index)
 {
 	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);

@@ -591,11 +591,8 @@ static int acpi_idle_play_dead(struct cp
 		else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
 			io_idle(cx->address);
 		} else
-			return -ENODEV;
+			return;
 	}
-
-	/* Never reached */
-	return 0;
 }

 static __always_inline bool acpi_idle_fallback_to_c1(struct acpi_processor *pr)