[v2,1/3] vt: add cursor blink interval escape sequence

Commit Message

Scot Doyle March 26, 2015, 1:54 p.m. UTC

Add an escape sequence to specify the current console's cursor blink
interval. The interval is specified as a number of milliseconds until
the next cursor display state toggle, from 50 to 65535. /proc/loadavg
did not show a difference with a one msec interval, but the lower
bound is set to 50 msecs since slower hardware wasn't tested.

Store the interval in the vc_data structure for later access by fbcon,
initializing the value to fbcon's current hardcoded value of 200 msecs.

Signed-off-by: Scot Doyle <[e-mail]>
Acked-by: Pavel Machek <[e-mail]>
---
 drivers/tty/vt/vt.c            | 9 +++++++++
 include/linux/console_struct.h | 1 +
 2 files changed, 10 insertions(+)

Comments

Mike Frysinger March 28, 2015, 12:35 a.m. UTC | #1

On 26 Mar 2015 13:54, Scot Doyle wrote:
> Add an escape sequence to specify the current console's cursor blink
> interval. The interval is specified as a number of milliseconds until
> the next cursor display state toggle, from 50 to 65535. /proc/loadavg
> did not show a difference with a one msec interval, but the lower
> bound is set to 50 msecs since slower hardware wasn't tested.

if they want to be crazy, why not let them ?  it's not like we generally prevent 
the user from destroying their machine.  i.e. just require the value to be > 0 
(unless you want to let 0 disable things).
-mike

Pavel Machek March 28, 2015, 7:50 a.m. UTC | #2

On Fri 2015-03-27 20:35:03, Mike Frysinger wrote:
> On 26 Mar 2015 13:54, Scot Doyle wrote:
> > Add an escape sequence to specify the current console's cursor blink
> > interval. The interval is specified as a number of milliseconds until
> > the next cursor display state toggle, from 50 to 65535. /proc/loadavg
> > did not show a difference with a one msec interval, but the lower
> > bound is set to 50 msecs since slower hardware wasn't tested.
> 
> if they want to be crazy, why not let them ?  it's not like we generally prevent 
> the user from destroying their machine.  i.e. just require the value to be > 0 
> (unless you want to let 0 disable things).

Because anyone with access to console can do this, and we only allow root
users to destroy the machine.
									Pavel

Patch

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 6e00572..ab1f173 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -135,6 +135,7 @@  const struct consw *conswitchp;
  */
 #define DEFAULT_BELL_PITCH	750
 #define DEFAULT_BELL_DURATION	(HZ/8)
+#define DEFAULT_CURSOR_BLINK_MS	200
 
 struct vc vc_cons [MAX_NR_CONSOLES];
 
@@ -1590,6 +1591,13 @@  static void setterm_command(struct vc_data *vc)
 		case 15: /* activate the previous console */
 			set_console(last_console);
 			break;
+		case 16: /* set cursor blink duration in msec */
+			if (vc->vc_npar >= 1 && vc->vc_par[1] >= 50 &&
+					vc->vc_par[1] <= USHRT_MAX)
+				vc->vc_cur_blink_ms = vc->vc_par[1];
+			else
+				vc->vc_cur_blink_ms = DEFAULT_CURSOR_BLINK_MS;
+			break;
 	}
 }
 
@@ -1717,6 +1725,7 @@  static void reset_terminal(struct vc_data *vc, int do_clear)
 
 	vc->vc_bell_pitch = DEFAULT_BELL_PITCH;
 	vc->vc_bell_duration = DEFAULT_BELL_DURATION;
+	vc->vc_cur_blink_ms = DEFAULT_CURSOR_BLINK_MS;
 
 	gotoxy(vc, 0, 0);
 	save_cur(vc);
diff --git a/include/linux/console_struct.h b/include/linux/console_struct.h
index e859c98..e329ee2 100644
--- a/include/linux/console_struct.h
+++ b/include/linux/console_struct.h
@@ -104,6 +104,7 @@  struct vc_data {
 	unsigned int    vc_resize_user;         /* resize request from user */
 	unsigned int	vc_bell_pitch;		/* Console bell pitch */
 	unsigned int	vc_bell_duration;	/* Console bell duration */
+	unsigned short	vc_cur_blink_ms;	/* Cursor blink duration */
 	struct vc_data **vc_display_fg;		/* [!] Ptr to var holding fg console for this display */
 	struct uni_pagedir *vc_uni_pagedir;
 	struct uni_pagedir **vc_uni_pagedir_loc; /* [!] Location of uni_pagedir variable for this console */