[PATCH] drm: don't add inferred modes for monitors that don't support them

[Alex Deucher]

On Fri, Feb 15, 2013 at 10:36 AM, Paulo Zanoni <przanoni at gmail.com> wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>
> If bit 0 of the features byte (0x18) is set to 0, then, according to
> the EDID spec, "the display is non-continuous frequency (multi-mode)
> and is only specified to accept the video timing formats that are
> listed in Base EDID and certain Extension Blocks".
>
> For more information, please see the EDID spec, check the notes of the
> table that explains the "Feature Support" byte (18h) and also the
> notes on the tables of the section that explains "Display Range Limits
> & Additional Timing Description Definition (tag #FDh)".
>
> Cc: Adam Jackson <ajax at redhat.com>
> Cc: stable at vger.kernel.org
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45729
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

I fixed this same bug years ago in the X server in the pre-KMS days.

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/drm_edid.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> I still need to ask some specific people to test the patch, but I
> believe it is correct.
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index a3a3b61..6a003b6 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -2053,7 +2053,8 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
>         num_modes += add_cvt_modes(connector, edid);
>         num_modes += add_standard_modes(connector, edid);
>         num_modes += add_established_modes(connector, edid);
> -       num_modes += add_inferred_modes(connector, edid);
> +       if (edid->features & DRM_EDID_FEATURE_DEFAULT_GTF)
> +               num_modes += add_inferred_modes(connector, edid);
>         num_modes += add_cea_modes(connector, edid);
>
>         if (quirks & (EDID_QUIRK_PREFER_LARGE_60 | EDID_QUIRK_PREFER_LARGE_75))
> --
> 1.7.10.4
>
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