xref: /openbmc/linux/kernel/power/console.c (revision 22246614)
1 /*
2  * drivers/power/process.c - Functions for saving/restoring console.
3  *
4  * Originally from swsusp.
5  */
6 
7 #include <linux/vt_kern.h>
8 #include <linux/kbd_kern.h>
9 #include <linux/console.h>
10 #include <linux/module.h>
11 #include "power.h"
12 
13 #if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
14 #define SUSPEND_CONSOLE	(MAX_NR_CONSOLES-1)
15 
16 static int orig_fgconsole, orig_kmsg;
17 static int disable_vt_switch;
18 
19 /*
20  * Normally during a suspend, we allocate a new console and switch to it.
21  * When we resume, we switch back to the original console.  This switch
22  * can be slow, so on systems where the framebuffer can handle restoration
23  * of video registers anyways, there's little point in doing the console
24  * switch.  This function allows you to disable it by passing it '0'.
25  */
26 void pm_set_vt_switch(int do_switch)
27 {
28 	acquire_console_sem();
29 	disable_vt_switch = !do_switch;
30 	release_console_sem();
31 }
32 EXPORT_SYMBOL(pm_set_vt_switch);
33 
34 int pm_prepare_console(void)
35 {
36 	acquire_console_sem();
37 
38 	if (disable_vt_switch) {
39 		release_console_sem();
40 		return 0;
41 	}
42 
43 	orig_fgconsole = fg_console;
44 
45 	if (vc_allocate(SUSPEND_CONSOLE)) {
46 	  /* we can't have a free VC for now. Too bad,
47 	   * we don't want to mess the screen for now. */
48 		release_console_sem();
49 		return 1;
50 	}
51 
52 	if (set_console(SUSPEND_CONSOLE)) {
53 		/*
54 		 * We're unable to switch to the SUSPEND_CONSOLE.
55 		 * Let the calling function know so it can decide
56 		 * what to do.
57 		 */
58 		release_console_sem();
59 		return 1;
60 	}
61 	release_console_sem();
62 
63 	if (vt_waitactive(SUSPEND_CONSOLE)) {
64 		pr_debug("Suspend: Can't switch VCs.");
65 		return 1;
66 	}
67 	orig_kmsg = kmsg_redirect;
68 	kmsg_redirect = SUSPEND_CONSOLE;
69 	return 0;
70 }
71 
72 void pm_restore_console(void)
73 {
74 	acquire_console_sem();
75 	if (disable_vt_switch) {
76 		release_console_sem();
77 		return;
78 	}
79 	set_console(orig_fgconsole);
80 	release_console_sem();
81 	kmsg_redirect = orig_kmsg;
82 }
83 #endif
84