How to find out modeline without attaching actual device?

[Bruno Prémont]

Hi Paul,

On Sun, 12 August 2012 Paul Menzel <paulepanter at users.sourceforge.net> wrote:
> Dear Linux folks,
> 
> regarding modelines problems with some TVs [1] and EDID quirks, Ian sent
> nice patches for [2], is there a way to test what modeline the DRM
> subsystem would choose without actually attaching the device?
> 
> The problem is, the TV is at a different place and I rarely have access
> to it. So it would be great if I could just use some kind of simulator
> and pass the EDID to it, what connector it is on (though this should not
> matter) and I get the calculated modeline as a result.
> 
> This should be enough since I already know what modeline works.

I think you can, by plugging a monitor of your choice and injecting the
EDID you want to test with drm_kms_helper's edid_firmware parameter.

It will then load the EDID from /lib/firmware/ instead of asking
the monitor.

Select CONFIG_DRM_LOAD_EDID_FIRMWARE, then when loading drm_kms_helper.ko
set edid_firmware=VGA1:edid/myedid.bin module option to load EDID from
/lib/firmware/edid/myedid.bin.

See also Documentation/EDID/HOWTO.txt

Bruno


> Thanks,
> 
> Paul
> 
> 
> [1] https://bugs.freedesktop.org/show_bug.cgi?id=26294
> [2] http://lists.freedesktop.org/archives/dri-devel/2012-August/026264.html