When some tiles of a tiled display are missing,
drm_client_firmware_config() replaces the connector's mode with
drm_connector_fallback_non_tiled_mode(). That returns NULL when
connector->modes has no mode other than the tile size, but the debug
message after it still reads modes[i]->name. Accessing a member through
a NULL pointer is undefined behaviour. Today printk happens to get an
address below PAGE_SIZE and prints "(efault)"
Print "(none)" as the mode name instead. A connector whose mode is NULL
is skipped by drm_client_modeset_probe(), so it is left off, as before
While at it, drop the extra colon in "[CONNECTOR::%d:%s]". Every other
DRM debug message prints [CONNECTOR:%d:%s], and the double colon breaks
grepping the log for a connector id
Sashiko found this while reviewing a series that makes the fallback
return NULL more often, by also skipping modes larger than the client
Fixes: cf1d0180f571 ("drm/fbdev: Fallback to non tiled mode if all tiles not
present")
Link: https://lore.kernel.org/all/[email protected]/
Suggested-by: Thomas Zimmermann <[email protected]>
Signed-off-by: Hugo Sales <[email protected]>
---
Changes in v2:
- Use modes[i] ? modes[i]->name : "(none)" in the existing message
instead of a second drm_dbg_kms() (Thomas)
- Drop the extra colon in "[CONNECTOR::%d:%s]" on the same line
- v1: https://lore.kernel.org/r/[email protected]
I ran checkpatch and built drm_client_modeset.o with W=1
drivers/gpu/drm/drm_client_modeset.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_client_modeset.c
b/drivers/gpu/drm/drm_client_modeset.c
index 0080a8e9556a..67f90e5d1512 100644
--- a/drivers/gpu/drm/drm_client_modeset.c
+++ b/drivers/gpu/drm/drm_client_modeset.c
@@ -754,10 +754,10 @@ static bool drm_client_firmware_config(struct
drm_client_dev *client,
}
crtcs[i] = crtc;
- drm_dbg_kms(dev, "[CONNECTOR::%d:%s] on [CRTC:%d:%s] using %s
mode: %s\n",
+ drm_dbg_kms(dev, "[CONNECTOR:%d:%s] on [CRTC:%d:%s] using %s
mode: %s\n",
connector->base.id, connector->name,
crtc->base.id, crtc->name,
- mode_type, modes[i]->name);
+ mode_type, modes[i] ? modes[i]->name : "(none)");
fallback = false;
conn_configured |= BIT(i);
--
2.55.0
