[PATCH] vt: Delay the update of the visible framebuffer console

[PATCH] vt: Delay the update of the visible framebuffer console

[Jordan Crouse]

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This is a patch that delays updating the visible framebuffer console
until the other consoles have been initialized in order to avoid losing
output lines.  This problem was discovered when loading a framebuffer driver
as a module.  Comments welcome.

Jordan

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[PATCH] vt:  Delay the update of the visible framebuffer console

From: David Hollister <david.hollister@amd.com>

This patch delays the update of the visible framebuffer console until
all other consoles have been initialized in order to avoid losing
information.  This only seems to be a problem with modules, not with
built-in drivers.

Signed-off-by: David Hollister <david.hollister@amd.com>
Signed-off-by: Jordan Crouse <jordan.crouse@amd.com>
---

 drivers/char/vt.c |   22 ++++++++++++++--------
 1 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index acc5d47..30f0f24 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -2700,9 +2700,11 @@ int take_over_console(const struct consw
 		if (!vc || !vc->vc_sw)
 			continue;
 
-		j = i;
-		if (CON_IS_VISIBLE(vc))
+		if (CON_IS_VISIBLE(vc)) {
+			j = i;
 			save_screen(vc);
+		}
+
 		old_was_color = vc->vc_can_do_color;
 		vc->vc_sw->con_deinit(vc);
 		vc->vc_origin = (unsigned long)vc->vc_screenbuf;
@@ -2718,17 +2720,21 @@ int take_over_console(const struct consw
 		 */
 		if (old_was_color != vc->vc_can_do_color)
 			clear_buffer_attributes(vc);
-
-		if (CON_IS_VISIBLE(vc))
-			update_screen(vc);
 	}
+
 	printk("Console: switching ");
 	if (!deflt)
 		printk("consoles %d-%d ", first+1, last+1);
-	if (j >= 0)
+	if (j >= 0) {
+		struct vc_data *vc = vc_cons[j].d;
+
 		printk("to %s %s %dx%d\n",
-		       vc_cons[j].d->vc_can_do_color ? "colour" : "mono",
-		       desc, vc_cons[j].d->vc_cols, vc_cons[j].d->vc_rows);
+		       vc->vc_can_do_color ? "colour" : "mono",
+		       desc, vc->vc_cols, vc->vc_rows);
+
+		if (CON_IS_VISIBLE(vc))
+			update_screen(vc);
+	}
 	else
 		printk("to %s\n", desc);
 

Re: [Linux-fbdev-devel] [PATCH] vt: Delay the update of the visible framebuffer console

[Antonino A. Daplas]

Jordan Crouse wrote:
> This is a patch that delays updating the visible framebuffer console
> until the other consoles have been initialized in order to avoid losing
> output lines.  This problem was discovered when loading a framebuffer driver
> as a module.  Comments welcome.
> 
> Jordan
> 
> 
> ------------------------------------------------------------------------
> 
> [PATCH] vt:  Delay the update of the visible framebuffer console
> 
> From: David Hollister <david.hollister@amd.com>
> 
> This patch delays the update of the visible framebuffer console until
> all other consoles have been initialized in order to avoid losing
> information.  This only seems to be a problem with modules, not with
> built-in drivers.

Looks okay except for one point...

> 
> Signed-off-by: David Hollister <david.hollister@amd.com>
> Signed-off-by: Jordan Crouse <jordan.crouse@amd.com>
> ---
> 
>  drivers/char/vt.c |   22 ++++++++++++++--------
>  1 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/vt.c b/drivers/char/vt.c
> index acc5d47..30f0f24 100644
> --- a/drivers/char/vt.c
> +++ b/drivers/char/vt.c
> @@ -2700,9 +2700,11 @@ int take_over_console(const struct consw
>  		if (!vc || !vc->vc_sw)
>  			continue;
>  
> -		j = i;
> -		if (CON_IS_VISIBLE(vc))
> +		if (CON_IS_VISIBLE(vc)) {
> +			j = i;
>  			save_screen(vc);
> +		}
> +
>  		old_was_color = vc->vc_can_do_color;
>  		vc->vc_sw->con_deinit(vc);
>  		vc->vc_origin = (unsigned long)vc->vc_screenbuf;
> @@ -2718,17 +2720,21 @@ int take_over_console(const struct consw
>  		 */
>  		if (old_was_color != vc->vc_can_do_color)
>  			clear_buffer_attributes(vc);
> -
> -		if (CON_IS_VISIBLE(vc))
> -			update_screen(vc);
>  	}
> +
>  	printk("Console: switching ");
>  	if (!deflt)
>  		printk("consoles %d-%d ", first+1, last+1);
> -	if (j >= 0)
> +	if (j >= 0) {
> +		struct vc_data *vc = vc_cons[j].d;
> +
>  		printk("to %s %s %dx%d\n",
> -		       vc_cons[j].d->vc_can_do_color ? "colour" : "mono",
> -		       desc, vc_cons[j].d->vc_cols, vc_cons[j].d->vc_rows);
> +		       vc->vc_can_do_color ? "colour" : "mono",
> +		       desc, vc->vc_cols, vc->vc_rows);
> +
> +		if (CON_IS_VISIBLE(vc))
> +			update_screen(vc);
> +	}
>  	else
>  		printk("to %s\n", desc);

If take_over_console() is called with parameter first = 0, last = 4, and
the visible console = 5, you get here instead...

Tony