lkml.org 
[lkml]   [2005]   [Dec]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/1 2.6.15-rc4-git1] Fix switching to KD_TEXT
Please do forget about that patch I sent to you some days ago. An 
enhanced version
will follow soon.

cu,
knut

Knut Petersen schrieb:

> Every framebuffer driver relies on the assumption that the set_par()
> function
> of the driver is called before drawing functions and other functions
> dependent
> on the hardware state are executed.
>
> This assumption is false in two cases, and one is a genuine linux
> bug:
>
> 1: Whenever you switch from X to a framebuffer console for the very
> first time, there is a chance that a broken X system has _not_ set
> the mode to KD_GRAPHICS, thus the vt and framebuffer code
> executes a screen redraw and several other functions before a
> set_par() is executed. This is believed to be not a bug of linux
> but a bug of X/xdm.
>
> 2: Whenever a switch from X to a framebuffer console occures,
> the pan_display() function of the driver is called once before
> the set_par() function of the driver is called. Code path:
> complete_change_console -> redraw_screen -> fbcon_switch ->
> bit_update_start-> fb_pan_display -> xyz_pan_display.
> This is clearly a bug of linux.
>
> Although our primary goal must be to fix linux bugs and not to work
> around bugs of X, the patch fixes both of the cases.
>
> The advantage and correctness of this patch should be obvious. Yes, it
> does add a possibly slow call to the fb_set_par() function, but at this
> point it is necessary.
>
> Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>
>
>
> diff -uprN -X linux/Documentation/dontdiff -x '*.bak' -x '*.ctx'
> linuxorig/drivers/video/console/fbcon.c
> linux/drivers/video/console/fbcon.c
> --- linuxorig/drivers/video/console/fbcon.c 2005-12-02
> 12:18:04.000000000 +0100
> +++ linux/drivers/video/console/fbcon.c 2005-12-06
> 09:06:56.000000000 +0100
> @@ -2103,10 +2103,11 @@ static int fbcon_switch(struct vc_data *
> fb_set_var(info, &var);
> ops->var = info->var;
>
> - if (old_info != NULL && old_info != info) {
> - if (info->fbops->fb_set_par)
> - info->fbops->fb_set_par(info);
> + if (old_info != NULL && old_info != info)
> fbcon_del_cursor_timer(old_info);
> +
> + if (info->fbops->fb_set_par) {
> + info->fbops->fb_set_par(info);
> fbcon_add_cursor_timer(info);
> }
>
>
>

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-12-10 07:30    [W:0.040 / U:2.936 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site