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>

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>
Samuel Thibault · Linus Torvalds
1 parent fe9d4f5763
Showing 3 changed files with 62 additions and 1 deletions Side-by-side Diff
drivers/char/vt.c
include/linux/notifier.h
include/linux/vt.h
@@ -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 @@
 };
  
 /*
+ * 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 @@
 		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 @@
 	    /* 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 @@
 	    }
 	    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 @@
  
 	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 @@
 		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 @@
 {
 	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 @@
 		vc->vc_pos -= 2;
 		vc->vc_x--;
 		vc->vc_need_wrap = 0;
+		notify_write(vc, '\b');
 	}
 }
  
@@ -1593,6 +1630,7 @@
 				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 @@
 				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 @@
 	release_console_sem();
  
 out:
+	notify_update(vc);
 	return n;
 #undef FLUSH
 }
@@ -2317,6 +2357,7 @@
 		do_blank_screen(0);
 		blank_timer_expired = 0;
 	}
+	notify_update(vc_cons[fg_console].d);
  
 	release_console_sem();
 }
@@ -2418,6 +2459,7 @@
 				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 @@
 		}
 	}
 	set_cursor(vc);
+	notify_update(vc);
  
 quit:
 	clear_bit(0, &printing);
@@ -242,6 +242,12 @@
  
 extern struct blocking_notifier_head reboot_notifier_list;
  
+/* 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 */
 #ifndef _LINUX_VT_H
 #define _LINUX_VT_H
  
+#ifdef __KERNEL__
+struct notifier_block;
+
+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).
...	...	@@ -99,6 +99,7 @@
99	99	#include <linux/pm.h>
100	100	#include <linux/font.h>
101	101	#include <linux/bitops.h>
	102	+#include <linux/notifier.h>
102	103
103	104	#include <asm/io.h>
104	105	#include <asm/system.h>
...	...	@@ -223,6 +224,35 @@
223	224	};
224	225
225	226	/*
	227	+ * Notifier list for console events.
	228	+ */
	229	+static ATOMIC_NOTIFIER_HEAD(vt_notifier_list);
	230	+
	231	+int register_vt_notifier(struct notifier_block *nb)
	232	+{
	233	+ return atomic_notifier_chain_register(&vt_notifier_list, nb);
	234	+}
	235	+EXPORT_SYMBOL_GPL(register_vt_notifier);
	236	+
	237	+int unregister_vt_notifier(struct notifier_block *nb)
	238	+{
	239	+ return atomic_notifier_chain_unregister(&vt_notifier_list, nb);
	240	+}
	241	+EXPORT_SYMBOL_GPL(unregister_vt_notifier);
	242	+
	243	+static void notify_write(struct vc_data *vc, unsigned int unicode)
	244	+{
	245	+ struct vt_notifier_param param = { .vc = vc, unicode = unicode };
	246	+ atomic_notifier_call_chain(&vt_notifier_list, VT_WRITE, &param);
	247	+}
	248	+
	249	+static void notify_update(struct vc_data *vc)
	250	+{
	251	+ struct vt_notifier_param param = { .vc = vc };
	252	+ atomic_notifier_call_chain(&vt_notifier_list, VT_UPDATE, &param);
	253	+}
	254	+
	255	+/*
226	256	* Low-Level Functions
227	257	*/
228	258
...	...	@@ -718,6 +748,7 @@
718	748	return -ENXIO;
719	749	if (!vc_cons[currcons].d) {
720	750	struct vc_data *vc;
	751	+ struct vt_notifier_param param;
721	752
722	753	/* prevent users from taking too much memory */
723	754	if (currcons >= MAX_NR_USER_CONSOLES && !capable(CAP_SYS_RESOURCE))
...	...	@@ -729,7 +760,7 @@
729	760	/* although the numbers above are not valid since long ago, the
730	761	point is still up-to-date and the comment still has its value
731	762	even if only as a historical artifact. --mj, July 1998 */
732		- vc = kzalloc(sizeof(struct vc_data), GFP_KERNEL);
	763	+ param.vc = vc = kzalloc(sizeof(struct vc_data), GFP_KERNEL);
733	764	if (!vc)
734	765	return -ENOMEM;
735	766	vc_cons[currcons].d = vc;
...	...	@@ -746,6 +777,7 @@
746	777	}
747	778	vc->vc_kmalloced = 1;
748	779	vc_init(vc, vc->vc_rows, vc->vc_cols, 1);
	780	+ atomic_notifier_call_chain(&vt_notifier_list, VT_ALLOCATE, &param);
749	781	}
750	782	return 0;
751	783	}
...	...	@@ -907,6 +939,8 @@
907	939
908	940	if (vc_cons_allocated(currcons)) {
909	941	struct vc_data *vc = vc_cons[currcons].d;
	942	+ struct vt_notifier_param param = { .vc = vc };
	943	+ atomic_notifier_call_chain(&vt_notifier_list, VT_DEALLOCATE, &param);
910	944	vc->vc_sw->con_deinit(vc);
911	945	put_pid(vc->vt_pid);
912	946	module_put(vc->vc_sw->owner);
...	...	@@ -1019,6 +1053,7 @@
1019	1053	vc->vc_pos += vc->vc_size_row;
1020	1054	}
1021	1055	vc->vc_need_wrap = 0;
	1056	+ notify_write(vc, '\n');
1022	1057	}
1023	1058
1024	1059	static void ri(struct vc_data *vc)
...	...	@@ -1039,6 +1074,7 @@
1039	1074	{
1040	1075	vc->vc_pos -= vc->vc_x << 1;
1041	1076	vc->vc_need_wrap = vc->vc_x = 0;
	1077	+ notify_write(vc, '\r');
1042	1078	}
1043	1079
1044	1080	static inline void bs(struct vc_data *vc)
...	...	@@ -1047,6 +1083,7 @@
1047	1083	vc->vc_pos -= 2;
1048	1084	vc->vc_x--;
1049	1085	vc->vc_need_wrap = 0;
	1086	+ notify_write(vc, '\b');
1050	1087	}
1051	1088	}
1052	1089
...	...	@@ -1593,6 +1630,7 @@
1593	1630	break;
1594	1631	}
1595	1632	vc->vc_pos += (vc->vc_x << 1);
	1633	+ notify_write(vc, '\t');
1596	1634	return;
1597	1635	case 10: case 11: case 12:
1598	1636	lf(vc);
...	...	@@ -2252,6 +2290,7 @@
2252	2290	tc = conv_uni_to_pc(vc, ' '); /* A space is printed in the second column */
2253	2291	if (tc < 0) tc = ' ';
2254	2292	}
	2293	+ notify_write(vc, c);
2255	2294
2256	2295	if (inverse) {
2257	2296	FLUSH
...	...	@@ -2274,6 +2313,7 @@
2274	2313	release_console_sem();
2275	2314
2276	2315	out:
	2316	+ notify_update(vc);
2277	2317	return n;
2278	2318	#undef FLUSH
2279	2319	}
...	...	@@ -2317,6 +2357,7 @@
2317	2357	do_blank_screen(0);
2318	2358	blank_timer_expired = 0;
2319	2359	}
	2360	+ notify_update(vc_cons[fg_console].d);
2320	2361
2321	2362	release_console_sem();
2322	2363	}
...	...	@@ -2418,6 +2459,7 @@
2418	2459	continue;
2419	2460	}
2420	2461	scr_writew((vc->vc_attr << 8) + c, (unsigned short *)vc->vc_pos);
	2462	+ notify_write(vc, c);
2421	2463	cnt++;
2422	2464	if (myx == vc->vc_cols - 1) {
2423	2465	vc->vc_need_wrap = 1;
...	...	@@ -2436,6 +2478,7 @@
2436	2478	}
2437	2479	}
2438	2480	set_cursor(vc);
	2481	+ notify_update(vc);
2439	2482
2440	2483	quit:
2441	2484	clear_bit(0, &printing);
...	...	@@ -242,6 +242,12 @@
242	242
243	243	extern struct blocking_notifier_head reboot_notifier_list;
244	244
	245	+/* Virtual Terminal events. */
	246	+#define VT_ALLOCATE 0x0001 /* Console got allocated */
	247	+#define VT_DEALLOCATE 0x0002 /* Console will be deallocated */
	248	+#define VT_WRITE 0x0003 /* A char got output */
	249	+#define VT_UPDATE 0x0004 /* A bigger update occurred */
	250	+
245	251	#endif /* __KERNEL__ */
246	252	#endif /* _LINUX_NOTIFIER_H */
1	1	#ifndef _LINUX_VT_H
2	2	#define _LINUX_VT_H
3	3
	4	+#ifdef __KERNEL__
	5	+struct notifier_block;
	6	+
	7	+struct vt_notifier_param {
	8	+ struct vc_data vc; / VC on which the update happened */
	9	+ unsigned int c; /* Printed char */
	10	+};
	11	+
	12	+extern int register_vt_notifier(struct notifier_block *nb);
	13	+extern int unregister_vt_notifier(struct notifier_block *nb);
	14	+#endif
	15	+
4	16	/*
5	17	* These constants are also useful for user-level apps (e.g., VC
6	18	* resizing).