Messages in this thread Patch in this message |  | | Date | Thu, 08 Dec 2005 23:49:44 +0100 | From | Knut Petersen <> | Subject | [PATCH 1/1 2.6.15-rc4-git1] Fix switching to KD_TEXT |
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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); }
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