linux-kernel - [PATCH v8 07/27] kernel/reboot: Add kernel_can_power

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Message-Id: <20220509233235.995021-8-dmitry.osipenko@collabora.com>
Date:   Tue, 10 May 2022 02:32:15 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Joshua Thompson <funaho@...ai.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Sebastian Reichel <sre@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
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        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
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        Lee Jones <lee.jones@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     linux-kernel@...r.kernel.org, linux-csky@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-sh@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-acpi@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: [PATCH v8 07/27] kernel/reboot: Add kernel_can_power_off()

Add kernel_can_power_off() helper that replaces open-coded checks of
the global pm_power_off variable. This is a necessary step towards
supporting chained power-off handlers.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
---
 include/linux/reboot.h |  1 +
 kernel/reboot.c        | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 6b951d68c0c7..c52f77ee4ddd 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -149,6 +149,7 @@ extern void kernel_restart_prepare(char *cmd);
 extern void kernel_restart(char *cmd);
 extern void kernel_halt(void);
 extern void kernel_power_off(void);
+extern bool kernel_can_power_off(void);
 
 void ctrl_alt_del(void);
 
diff --git a/kernel/reboot.c b/kernel/reboot.c
index eaede35f45e2..982e58c11ce8 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -523,6 +523,18 @@ void do_kernel_power_off(void)
 	atomic_notifier_call_chain(&power_off_handler_list, 0, NULL);
 }
 
+/**
+ *	kernel_can_power_off - check whether system can be powered off
+ *
+ *	Returns true if power-off handler is registered and system can be
+ *	powered off, false otherwise.
+ */
+bool kernel_can_power_off(void)
+{
+	return !atomic_notifier_call_chain_is_empty(&power_off_handler_list);
+}
+EXPORT_SYMBOL_GPL(kernel_can_power_off);
+
 /**
  *	kernel_power_off - power_off the system
  *
@@ -581,7 +593,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 	/* Instead of trying to make the power_off code look like
 	 * halt when pm_power_off is not set do it the easy way.
 	 */
-	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
+	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !kernel_can_power_off())
 		cmd = LINUX_REBOOT_CMD_HALT;
 
 	mutex_lock(&system_transition_mutex);
-- 
2.35.1