On 4/26/2022 1:21 PM, Douglas Anderson wrote:
If we're unable to read the EDID for a display because it's corrupt /
bogus / invalid then we'll add a set of standard modes for the
display. When userspace looks at these modes it doesn't really have a
good concept for which mode to pick and it'll likely pick the highest
resolution one by default. That's probably not ideal because the modes
were purely guesses on the part of the Linux kernel.
Let's instead set 640x480 as the "preferred" mode when we have no EDID.
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
drm_dmt_modes array is sorted but you are also relying on this check to
eliminate the non-60fps modes
5611 if (drm_mode_vrefresh(ptr) > 61)
5612 continue;
I am not sure why we filter out the modes > 61 vrefresh.
If that check will remain this is okay.
If its not, its not reliable that the first mode will be 640x480@60
---
drivers/gpu/drm/drm_edid.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 7a8482b75071..64ccfff4167e 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5839,6 +5839,15 @@ int drm_add_modes_noedid(struct drm_connector *connector,
continue;
mode = drm_mode_duplicate(dev, ptr);
if (mode) {
+ /*
+ * The drm_dmt_modes array is sorted so that lower
+ * resolutions come first. We'll set the lowest
+ * resolution mode as preferred. We have no EDID so
+ * we should prefer the lowest resolution mode as
+ * the safest one.
+ */
+ if (num_modes == 0)
+ mode->type |= DRM_MODE_TYPE_PREFERRED;
drm_mode_probed_add(connector, mode);
num_modes++;
}
