[PATCH] VT notifier extension for accessibility

[Samuel Thibault]

Some accessibility modules need to be able to catch the output on the
console before the VT interpretation, and possibly swallow it.

Signed-off-by: Samuel Thibault <[EMAIL PROTECTED]>
From: Karl Dahlke <[EMAIL PROTECTED]>

--- include/linux/notifier.h    2008-02-15 08:44:10.000000000 -0500
+++ include/linux/notifier.h.new        2008-02-15 09:58:00.000000000 -0500
@@ -247,6 +247,7 @@ extern struct blocking_notifier_head reb
 #define VT_DEALLOCATE          0x0002 /* Console will be deallocated */
 #define VT_WRITE               0x0003 /* A char got output */
 #define VT_UPDATE              0x0004 /* A bigger update occurred */
+#define VT_PREWRITE            0x0005 /* A char is about to be written to the 
console */
 
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */
--- drivers/char/vt.c   2008-02-15 08:43:35.000000000 -0500
+++ drivers/char/vt.c.new       2008-02-15 10:11:14.000000000 -0500
@@ -2053,6 +2053,7 @@ static int do_con_write(struct tty_struc
        unsigned long draw_from = 0, draw_to = 0;
        struct vc_data *vc;
        unsigned char vc_attr;
+       struct vt_notifier_param param;
        uint8_t rescan;
        uint8_t inverse;
        uint8_t width;
@@ -2112,6 +2113,8 @@ static int do_con_write(struct tty_struc
        if (IS_FG(vc))
                hide_cursor(vc);
 
+       param.vc = vc;
+
        while (!tty->stopped && count) {
                int orig = *buf;
                c = orig;
@@ -2200,6 +2203,10 @@ rescan_last_byte:
                    tc = vc->vc_translate[vc->vc_toggle_meta ? (c | 0x80) : c];
                }
 
+               param.c = tc;
+               if (atomic_notifier_call_chain(&vt_notifier_list, VT_PREWRITE, 
&param) == NOTIFY_STOP)
+                       continue;
+
                 /* If the original code was a control character we
                  * only allow a glyph to be displayed if the code is
                  * not normally used (such as for cursor movement) or
--
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