If the VGA connector has no DDC channel, an error pointer will be dereferenced, e.g. on Salvator-XS:
Unable to handle kernel NULL pointer dereference at virtual address 000000000000017d ... Call trace: sysfs_do_create_link_sd.isra.0+0x40/0x108 sysfs_create_link+0x20/0x40 drm_sysfs_connector_add+0xa8/0xc8 drm_connector_register.part.3+0x54/0xb0 drm_connector_register_all+0xb0/0xd0 drm_modeset_register_all+0x54/0x88 drm_dev_register+0x18c/0x1d8 rcar_du_probe+0xe4/0x150 ...
This happens because vga->ddc either contains a valid DDC channel pointer, or -ENODEV, and drm_connector_init_with_ddc() expects a valid DDC channel pointer, or NULL.
Fix this by resetting vga->ddc to NULL in case of -ENODEV, and replacing the existing error checks by non-NULL checks. This is similar to what the HDMI connector driver does.
Fixes: a4f9087e85de141e ("drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory") Signed-off-by: Geert Uytterhoeven geert+renesas@glider.be --- An alternative would be to check if vga->ddc contains an error pointer, and calling drm_connector_init() instead of drm_connector_init_with_ddc(), like before. --- drivers/gpu/drm/bridge/dumb-vga-dac.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c b/drivers/gpu/drm/bridge/dumb-vga-dac.c index 8ef6539ae78a6eb3..7aa789c358829b05 100644 --- a/drivers/gpu/drm/bridge/dumb-vga-dac.c +++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c @@ -42,7 +42,7 @@ static int dumb_vga_get_modes(struct drm_connector *connector) struct edid *edid; int ret;
- if (IS_ERR(vga->ddc)) + if (!vga->ddc) goto fallback;
edid = drm_get_edid(connector, vga->ddc); @@ -84,7 +84,7 @@ dumb_vga_connector_detect(struct drm_connector *connector, bool force) * wire the DDC pins, or the I2C bus might not be working at * all. */ - if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc)) + if (vga->ddc && drm_probe_ddc(vga->ddc)) return connector_status_connected;
return connector_status_unknown; @@ -197,6 +197,7 @@ static int dumb_vga_probe(struct platform_device *pdev) if (PTR_ERR(vga->ddc) == -ENODEV) { dev_dbg(&pdev->dev, "No i2c bus specified. Disabling EDID readout\n"); + vga->ddc = NULL; } else { dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n"); return PTR_ERR(vga->ddc); @@ -218,7 +219,7 @@ static int dumb_vga_remove(struct platform_device *pdev)
drm_bridge_remove(&vga->bridge);
- if (!IS_ERR(vga->ddc)) + if (vga->ddc) i2c_put_adapter(vga->ddc);
return 0;