Console events and accessibility

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.)

[akpm@linux-foundation.org: fix headers_check]
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 44 insertions, 1 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 1764c67b585f..7a5badfb7d84 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;
 }
@@ -907,6 +939,8 @@ 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);
@@ -1019,6 +1053,7 @@ 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)
@@ -1039,6 +1074,7 @@ 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)
@@ -1047,6 +1083,7 @@ static inline void bs(struct vc_data *vc)
                 vc->vc_pos -= 2;
                 vc->vc_x--;
                 vc->vc_need_wrap = 0;
+                notify_write(vc, '\b');
         }
 }
 
@@ -1593,6 +1630,7 @@ 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);
@@ -2252,6 +2290,7 @@ 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
@@ -2274,6 +2313,7 @@ rescan_last_byte:
         release_console_sem();
 
 out:
+        notify_update(vc);
         return n;
 #undef FLUSH
 }
@@ -2317,6 +2357,7 @@ 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();
 }
@@ -2418,6 +2459,7 @@ 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;
@@ -2436,6 +2478,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
                 }
         }
         set_cursor(vc);
+        notify_update(vc);
 
 quit:
         clear_bit(0, &printing);