[PATCH] Console events and accessibility

From: Samuel Thibault
Date: Tue Aug 21 2007 - 17:30:36 EST

Some external modules like Speakup need to monitor console output.

This adds a VT notifier that such modules can use to get console output events:
allocation, deallocation, writes, other updates (cursor position, switch, etc.)

Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>

---

This is the second hook for Speakup. I've already set symbols exported
to GPL only.

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index c20773a..8b87263 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -99,6 +99,7 @@
#include <linux/pm.h>
#include <linux/font.h>
#include <linux/bitops.h>
+#include <linux/notifier.h>

#include <asm/io.h>
#include <asm/system.h>
@@ -223,6 +224,35 @@ enum {
};

/*
+ * Notifier list for console events.
+ */
+static ATOMIC_NOTIFIER_HEAD(vt_notifier_list);
+
+int register_vt_notifier(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_register(&vt_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_vt_notifier);
+
+int unregister_vt_notifier(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_unregister(&vt_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_vt_notifier);
+
+static void notify_write(struct vc_data *vc, unsigned int unicode)
+{
+ struct vt_notifier_param param = { .vc = vc, unicode = unicode };
+ atomic_notifier_call_chain(&vt_notifier_list, VT_WRITE, &param);
+}
+
+static void notify_update(struct vc_data *vc)
+{
+ struct vt_notifier_param param = { .vc = vc };
+ atomic_notifier_call_chain(&vt_notifier_list, VT_UPDATE, &param);
+}
+
+/*
* Low-Level Functions
*/

@@ -718,6 +748,7 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */
return -ENXIO;
if (!vc_cons[currcons].d) {
struct vc_data *vc;
+ struct vt_notifier_param param;

/* prevent users from taking too much memory */
if (currcons >= MAX_NR_USER_CONSOLES && !capable(CAP_SYS_RESOURCE))
@@ -729,7 +760,7 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */
/* although the numbers above are not valid since long ago, the
point is still up-to-date and the comment still has its value
even if only as a historical artifact. --mj, July 1998 */
- vc = kzalloc(sizeof(struct vc_data), GFP_KERNEL);
+ param.vc = vc = kzalloc(sizeof(struct vc_data), GFP_KERNEL);
if (!vc)
return -ENOMEM;
vc_cons[currcons].d = vc;
@@ -746,6 +777,7 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */
}
vc->vc_kmalloced = 1;
vc_init(vc, vc->vc_rows, vc->vc_cols, 1);
+ atomic_notifier_call_chain(&vt_notifier_list, VT_ALLOCATE, &param);
}
return 0;
}
@@ -902,6 +934,8 @@ void vc_deallocate(unsigned int currcons)

if (vc_cons_allocated(currcons)) {
struct vc_data *vc = vc_cons[currcons].d;
+ struct vt_notifier_param param = { .vc = vc };
+ atomic_notifier_call_chain(&vt_notifier_list, VT_DEALLOCATE, &param);
vc->vc_sw->con_deinit(vc);
put_pid(vc->vt_pid);
module_put(vc->vc_sw->owner);
@@ -1014,6 +1048,7 @@ static void lf(struct vc_data *vc)
vc->vc_pos += vc->vc_size_row;
}
vc->vc_need_wrap = 0;
+ notify_write(vc, '\n');
}

static void ri(struct vc_data *vc)
@@ -1034,6 +1069,7 @@ static inline void cr(struct vc_data *vc)
{
vc->vc_pos -= vc->vc_x << 1;
vc->vc_need_wrap = vc->vc_x = 0;
+ notify_write(vc, '\r');
}

static inline void bs(struct vc_data *vc)
@@ -1042,6 +1078,7 @@ static inline void bs(struct vc_data *vc)
vc->vc_pos -= 2;
vc->vc_x--;
vc->vc_need_wrap = 0;
+ notify_write(vc, '\b');
}
}

@@ -1588,6 +1625,7 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
break;
}
vc->vc_pos += (vc->vc_x << 1);
+ notify_write(vc, '\t');
return;
case 10: case 11: case 12:
lf(vc);
@@ -2247,6 +2285,7 @@ rescan_last_byte:
tc = conv_uni_to_pc(vc, ' '); /* A space is printed in the second column */
if (tc < 0) tc = ' ';
}
+ notify_write(vc, c);

if (inverse) {
FLUSH
@@ -2269,6 +2308,7 @@ rescan_last_byte:
release_console_sem();

out:
+ notify_update(vc);
return n;
#undef FLUSH
}
@@ -2312,6 +2352,7 @@ static void console_callback(struct work_struct *ignored)
do_blank_screen(0);
blank_timer_expired = 0;
}
+ notify_update(vc_cons[fg_console].d);

release_console_sem();
}
@@ -2413,6 +2454,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
continue;
}
scr_writew((vc->vc_attr << 8) + c, (unsigned short *)vc->vc_pos);
+ notify_write(vc, c);
cnt++;
if (myx == vc->vc_cols - 1) {
vc->vc_need_wrap = 1;
@@ -2431,6 +2473,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
}
}
set_cursor(vc);
+ notify_update(vc);

quit:
clear_bit(0, &printing);
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index bd37880..fb88436 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -240,5 +240,11 @@ static inline int notifier_to_errno(int ret)
#define KBD_KEYSYM 0x0004 /* Keyboard keysym */
#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */

+/* Virtual Terminal events. */
+#define VT_ALLOCATE 0x0001 /* Console got allocated */
+#define VT_DEALLOCATE 0x0002 /* Console will be deallocated */
+#define VT_WRITE 0x0003 /* A char got output */
+#define VT_UPDATE 0x0004 /* A bigger update occurred */
+
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
diff --git a/include/linux/vt.h b/include/linux/vt.h
index ba806e8..40216b0 100644
--- a/include/linux/vt.h
+++ b/include/linux/vt.h
@@ -1,6 +1,18 @@
#ifndef _LINUX_VT_H
#define _LINUX_VT_H

+#ifdef __KERNEL__
+#include <linux/notifier.h>
+
+struct vt_notifier_param {
+ struct vc_data *vc; /* VC on which the update happened */
+ unsigned int c; /* Printed char */
+};
+
+extern int register_vt_notifier(struct notifier_block *nb);
+extern int unregister_vt_notifier(struct notifier_block *nb);
+#endif
+
/*
* These constants are also useful for user-level apps (e.g., VC
* resizing).
-
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