tty: vt, cleanup and document con_scroll

Scrolling helpers scrup and scrdown both accept 'top' and 'bottom' as
unsigned int. Number of lines 'nr' is accepted as int, but all callers
pass down unsigned too. So change the type of 'nr' to unsigned too.
Now, promote unsigned int from the helpers up to the con_scroll
hook which actually accepted all those as signed int.

Next, the 'dir' parameter can have only two values and we define
constants for that: SM_UP and SM_DOWN. Switch them to enum and do
proper type checking on 'dir' too.

Finally, document the behaviour of the hook.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: <linux-fbdev@vger.kernel.org>
Cc: <linux-usb@vger.kernel.org>
Cc: <linux-parisc@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 5 deletions

diff --git a/include/linux/console.h b/include/linux/console.h
index 3672809234a7..508b012bd5bd 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -28,9 +28,17 @@ struct tty_struct;
 #define VT100ID "\033[?1;2c"
 #define VT102ID "\033[?6c"
 
+enum con_scroll {
+	SM_UP,
+	SM_DOWN,
+};
+
 /**
  * struct consw - callbacks for consoles
  *
+ * @con_scroll: move lines from @top to @bottom in direction @dir by @lines.
+ *		Return true if no generic handling should be done.
+ *		Invoked by csi_M and printing to the console.
  * @con_set_palette: sets the palette of the console to @table (optional)
  * @con_scrolldelta: the contents of the console should be scrolled by @lines.
  *		     Invoked by user. (optional)
@@ -44,7 +52,9 @@ struct consw {
 	void	(*con_putc)(struct vc_data *, int, int, int);
 	void	(*con_putcs)(struct vc_data *, const unsigned short *, int, int, int);
 	void	(*con_cursor)(struct vc_data *, int);
-	int	(*con_scroll)(struct vc_data *, int, int, int, int);
+	bool	(*con_scroll)(struct vc_data *, unsigned int top,
+			unsigned int bottom, enum con_scroll dir,
+			unsigned int lines);
 	int	(*con_switch)(struct vc_data *);
 	int	(*con_blank)(struct vc_data *, int, int);
 	int	(*con_font_set)(struct vc_data *, struct console_font *, unsigned);
@@ -99,10 +109,6 @@ static inline int con_debug_leave(void)
 }
 #endif
 
-/* scroll */
-#define SM_UP       (1)
-#define SM_DOWN     (2)
-
 /* cursor */
 #define CM_DRAW     (1)
 #define CM_ERASE    (2)