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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>
This commit is contained in:
Samuel Thibault 2007-10-18 23:39:17 -07:00 committed by Linus Torvalds
parent fe9d4f5763
commit b293d75847
3 changed files with 62 additions and 1 deletions
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45
drivers/char/vt.c
View File

@ -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>
@ -222,6 +223,35 @@ enum {
blank_vesa_wait,
};
/*
* 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);

6
include/linux/notifier.h
View File

@ -242,5 +242,11 @@ static inline int notifier_to_errno(int ret)
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 */

12
include/linux/vt.h
View File

@ -1,6 +1,18 @@
#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).