DDC overules xorg.conf displaysize

Remy Bosch remybosch at zonnet.nl
Mon May 7 03:22:34 PDT 2007

Remy Bosch wrote:
> Hi, all.
> I'm using xorg-server- and found that DDC overrules the
> DisplaySize option in xorg.conf. Shouldn't variables be tested before
> their value is overwritten?
> If we look in hw/xfree86/ddc/ddcProperty.c from line 317:
>     Monitor->widthmm = 10 * DDC->features.hsize;
>     Monitor->heightmm = 10 * DDC->features.vsize;
> These lines bluntly overwrite the value written without testing.
> By just checking for a value in Monitor->widthmm and Monitor->heightmm
> you can prevent overwriting the size of the config.
> Like this:
>     if (Monitor->widthmm <= 0)
>         Monitor->widthmm = 10 * DDC->features.hsize;
>     if (Monitor->heightmm <= 0)
>         Monitor->heightmm = 10 * DDC->features.vsize;

I cound't find any other thing getting overwritten, though I'm not too
familiar with the code. The function where this bug was found is

I have to set questionmarks at the following line in the same function
right after the displaysizes are set:
    /* If this is a digital display, then we can use reduced blanking */
    if (DDC->features.input_type)
        Monitor->reducedblanking = TRUE;
    /* Allow the user to also enable this through config */


I see no indication that a value from config is used to enable reduced


Remy Bosch

More information about the xorg mailing list