[lkml]   [2005]   [Dec]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Patch in this message
    Subject[PATCH 1/1 2.6.15-rc4-git1] Fix switching to KD_TEXT
      Every framebuffer driver relies on the assumption that the set_par() 
    of the driver is called before drawing functions and other functions
    on the hardware state are executed.

    This assumption is false in two cases, and one is a genuine linux

    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 <>

    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)
    + if (info->fbops->fb_set_par) {
    + info->fbops->fb_set_par(info);

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-12-09 00:42    [W:0.023 / U:0.056 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site