commit 0341a4d0fdd2a0a3d9e2bb3a9afef9f8292c8502
author Karl Dahlke <eklhad@comcast.net> Mon Apr 28 02:14:25 2008 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Mon Apr 28 08:58:32 2008 -0700
tree e073b06ad0d0e4a7d3aaed487db0655feadb31bb
parent f7440b0ecdeb3a04d07c546d02d29700d2a574b7

VT notifier extension for accessibility

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

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/vt.c

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 9b58b89..df4c3ea 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -2054,6 +2054,7 @@
 	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;
@@ -2113,6 +2114,8 @@
 	if (IS_FG(vc))
 		hide_cursor(vc);
 
+	param.vc = vc;
+
 	while (!tty->stopped && count) {
 		int orig = *buf;
 		c = orig;
@@ -2201,6 +2204,11 @@
 		    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

include/linux/notifier.h

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index f4df400..20dfed5 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -247,6 +247,7 @@
 #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 */