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Subject[PATCH 1/2] Introduce and use vt_kmsg_redirect() function
Date
Instead of using and exporting a global value kmsg_redirect, introduce a
function vt_kmsg_redirect() that both can set and return the console where
messages are printed.

Change all users of kmsg_redirect (the VT code itself and kernel/power.c)
to the new interface.

The main advantage is that vt_kmsg_redirect() can also be used when
CONFIG_VT_CONSOLE is not set.


Signed-off-by: Bernhard Walle <bernhard@bwalle.de>
---
drivers/char/vt.c | 43 +++++++++++++++++++++++++++++++++++++------
include/linux/tty.h | 2 --
include/linux/vt.h | 15 +++++++++++++++
kernel/power/console.c | 7 +++----
4 files changed, 55 insertions(+), 12 deletions(-)
diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 0c80c68..197fec5 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -182,12 +182,10 @@ static DECLARE_WORK(console_work, console_callback);
* fg_console is the current virtual console,
* last_console is the last used one,
* want_console is the console we want to switch to,
- * kmsg_redirect is the console for kernel messages,
*/
int fg_console;
int last_console;
int want_console = -1;
-int kmsg_redirect;

/*
* For each existing display, we have a pointer to console currently visible
@@ -2426,6 +2424,37 @@ struct tty_driver *console_driver;

#ifdef CONFIG_VT_CONSOLE

+/**
+ * vt_kmsg_redirect() - Sets/gets the kernel message console
+ * @new: The new virtual terminal number or -1 if the console should stay
+ * unchanged
+ *
+ * By default, the kernel messages are always printed on the current virtual
+ * console. However, the user may modify that default with the
+ * TIOCL_SETKMSGREDIRECT ioctl call.
+ *
+ * This function sets the kernel message console to be @new. It returns the old
+ * virtual console number. The virtual terminal number 0 (both as parameter and
+ * return value) means no redirection (i.e. always printed on the currently
+ * active console).
+ *
+ * The parameter -1 means that only the current console is returned, but the
+ * value is not modified. You may use the macro vt_get_kmsg_redirect() in that
+ * case to make the code more understandable.
+ *
+ * When the kernel is compiled without CONFIG_VT_CONSOLE, this function ignores
+ * the parameter and always returns 0.
+ */
+int vt_kmsg_redirect(int new)
+{
+ static int kmsg_con;
+
+ if (new != -1)
+ return xchg(&kmsg_con, new);
+ else
+ return kmsg_con;
+}
+
/*
* Console on virtual terminal
*
@@ -2440,6 +2469,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
const ushort *start;
ushort cnt = 0;
ushort myx;
+ int kmsg_console;

/* console busy or not yet initialized */
if (!printable)
@@ -2447,8 +2477,9 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
if (!spin_trylock(&printing_lock))
return;

- if (kmsg_redirect && vc_cons_allocated(kmsg_redirect - 1))
- vc = vc_cons[kmsg_redirect - 1].d;
+ kmsg_console = vt_get_kmsg_redirect();
+ if (kmsg_console && vc_cons_allocated(kmsg_console - 1))
+ vc = vc_cons[kmsg_console - 1].d;

/* read `x' only after setting currcons properly (otherwise
the `x' macro will read the x of the foreground console). */
@@ -2605,7 +2636,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
ret = set_vesa_blanking(p);
break;
case TIOCL_GETKMSGREDIRECT:
- data = kmsg_redirect;
+ data = vt_get_kmsg_redirect();
ret = __put_user(data, p);
break;
case TIOCL_SETKMSGREDIRECT:
@@ -2615,7 +2646,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
if (get_user(data, p+1))
ret = -EFAULT;
else
- kmsg_redirect = data;
+ vt_kmsg_redirect(data);
}
break;
case TIOCL_GETFGCONSOLE:
diff --git a/include/linux/tty.h b/include/linux/tty.h
index f0f43d0..fddafcb 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -340,8 +340,6 @@ extern void tty_write_flush(struct tty_struct *);

extern struct ktermios tty_std_termios;

-extern int kmsg_redirect;
-
extern void console_init(void);
extern int vcs_init(void);

diff --git a/include/linux/vt.h b/include/linux/vt.h
index 7afca0d..1ae127d 100644
--- a/include/linux/vt.h
+++ b/include/linux/vt.h
@@ -84,4 +84,19 @@ struct vt_setactivate {

#define VT_SETACTIVATE 0x560F /* Activate and set the mode of a console */

+#ifdef CONFIG_VT_CONSOLE
+
+extern int vt_kmsg_redirect(int new);
+
+#else
+
+static inline int vt_kmsg_redirect(int new)
+{
+ return 0;
+}
+
+#endif
+
+#define vt_get_kmsg_redirect() vt_kmsg_redirect(-1)
+
#endif /* _LINUX_VT_H */
diff --git a/kernel/power/console.c b/kernel/power/console.c
index 5187136..218e5af 100644
--- a/kernel/power/console.c
+++ b/kernel/power/console.c
@@ -6,7 +6,7 @@

#include <linux/vt_kern.h>
#include <linux/kbd_kern.h>
-#include <linux/console.h>
+#include <linux/vt.h>
#include <linux/module.h>
#include "power.h"

@@ -21,8 +21,7 @@ int pm_prepare_console(void)
if (orig_fgconsole < 0)
return 1;

- orig_kmsg = kmsg_redirect;
- kmsg_redirect = SUSPEND_CONSOLE;
+ orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
return 0;
}

@@ -30,7 +29,7 @@ void pm_restore_console(void)
{
if (orig_fgconsole >= 0) {
vt_move_to_console(orig_fgconsole, 0);
- kmsg_redirect = orig_kmsg;
+ vt_kmsg_redirect(orig_kmsg);
}
}
#endif
--
1.6.3.3


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