linux-kernel - [PATCH 1/2] PM: make VT switching to the suspend console optional

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Message-Id: <1351892621-4840-2-git-send-email-jbarnes@virtuousgeek.org>
Date:	Fri,  2 Nov 2012 14:43:40 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:	rjw@...k.pl
Subject: [PATCH 1/2] PM: make VT switching to the suspend console optional

KMS drivers can potentially restore the display configuration without
userspace help.  Such drivers can set a new global, pm_vt_switch, to
false if they support this feature.  In that case, the PM layer won't VT
switch to the suspend console at suspend time and then back to the
original VT on resume, but rather leave things alone for a nicer looking
suspend and resume sequence.

Signed-off-by: Jesse Barnes <jbarnes@...tuousgeek.org>
---
 include/linux/pm.h     |    3 +++
 kernel/power/console.c |    7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/pm.h b/include/linux/pm.h
index 007e687..d8e7efb 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -35,6 +35,9 @@ extern void (*pm_idle)(void);
 extern void (*pm_power_off)(void);
 extern void (*pm_power_off_prepare)(void);
 
+/* VT switch to the suspend console or not */
+extern bool pm_vt_switch; /* defaults to true in console.c */
+
 /*
  * Device power management
  */
diff --git a/kernel/power/console.c b/kernel/power/console.c
index b1dc456..65376b4 100644
--- a/kernel/power/console.c
+++ b/kernel/power/console.c
@@ -13,9 +13,13 @@
 #define SUSPEND_CONSOLE	(MAX_NR_CONSOLES-1)
 
 static int orig_fgconsole, orig_kmsg;
+bool pm_vt_switch = true;
 
 int pm_prepare_console(void)
 {
+	if (!pm_vt_switch)
+		return 0;
+
 	orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
 	if (orig_fgconsole < 0)
 		return 1;
@@ -26,6 +30,9 @@ int pm_prepare_console(void)
 
 void pm_restore_console(void)
 {
+	if (!pm_vt_switch)
+		return;
+
 	if (orig_fgconsole >= 0) {
 		vt_move_to_console(orig_fgconsole, 0);
 		vt_kmsg_redirect(orig_kmsg);
-- 
1.7.9.5

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