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drm/ast: Handle failed I2C initialization gracefully 

I2C initialization is allowed to fail. In this case, create a connector
without DDC adapter. The current code would dereference a NULL pointer.

Reading the modes from the connector is supposed to work without I2C
adapter. Add the respective test.

v2:
	* init edid to NULL to avoid uninitialized read (Dan)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20211206091125.29501-2-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2021-12-06 10:11:23 +01:00
parent d619f38c01
commit 55dc449a7c
1 changed files with 10 additions and 7 deletions
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17
drivers/gpu/drm/ast/ast_mode.c
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@ -1210,9 +1210,9 @@ static int ast_get_modes(struct drm_connector *connector)
{ {
struct ast_connector *ast_connector = to_ast_connector(connector); struct ast_connector *ast_connector = to_ast_connector(connector);
struct ast_private *ast = to_ast_private(connector->dev); struct ast_private *ast = to_ast_private(connector->dev);
struct edid *edid; struct edid *edid = NULL;
int ret;
bool flags = false; bool flags = false;
int ret;
if (ast->tx_chip_type == AST_TX_DP501) { if (ast->tx_chip_type == AST_TX_DP501) {
ast->dp501_maxclk = 0xff; ast->dp501_maxclk = 0xff;
@ -1226,7 +1226,7 @@ static int ast_get_modes(struct drm_connector *connector)
else else
kfree(edid); kfree(edid);
} }
if (!flags) if (!flags && ast_connector->i2c)
edid = drm_get_edid(connector, &ast_connector->i2c->adapter); edid = drm_get_edid(connector, &ast_connector->i2c->adapter);
if (edid) { if (edid) {
drm_connector_update_edid_property(&ast_connector->base, edid); drm_connector_update_edid_property(&ast_connector->base, edid);
@ -1332,10 +1332,13 @@ static int ast_connector_init(struct drm_device *dev)
if (!ast_connector->i2c) if (!ast_connector->i2c)
drm_err(dev, "failed to add ddc bus for connector\n"); drm_err(dev, "failed to add ddc bus for connector\n");
drm_connector_init_with_ddc(dev, connector, if (ast_connector->i2c)
&ast_connector_funcs, drm_connector_init_with_ddc(dev, connector, &ast_connector_funcs,
DRM_MODE_CONNECTOR_VGA, DRM_MODE_CONNECTOR_VGA,
&ast_connector->i2c->adapter); &ast_connector->i2c->adapter);
else
drm_connector_init(dev, connector, &ast_connector_funcs,
DRM_MODE_CONNECTOR_VGA);
drm_connector_helper_add(connector, &ast_connector_helper_funcs); drm_connector_helper_add(connector, &ast_connector_helper_funcs);