[PATCH v5 12/13] drm/ast: Implement polling for VGA and SIL164 connectors

[Thomas Zimmermann <tzimmermann@suse.de>]

Implement polling for VGA and SIL164 connectors. Set the flag
DRM_CONNECTOR_POLL_DISCONNECT for each to detect the removal of the
monitor cable. Implement struct drm_connector_helper_funcs.detect_ctx
for each type of connector by testing for EDID data.

The helper drm_connector_helper_detect_ctx() implements .detect_ctx()
on top of the connector's DDC channel. The function can be used by
other drivers as companion to drm_connector_helper_get_modes().

v5:
- share implementation in drm_connector_helper_detect_ctx() (Maxime)
- test for DDC presence with drm_probe_ddc() (Maxime, Jani)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/ast/ast_mode.c     |  6 ++++--
 drivers/gpu/drm/drm_probe_helper.c | 29 +++++++++++++++++++++++++++++
 include/drm/drm_probe_helper.h     |  3 +++
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index 71cc681d6188f..a42a0956c51de 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -1346,6 +1346,7 @@ static int ast_crtc_init(struct drm_device *dev)
 
 static const struct drm_connector_helper_funcs ast_vga_connector_helper_funcs = {
 	.get_modes = drm_connector_helper_get_modes,
+	.detect_ctx = drm_connector_helper_detect_ctx,
 };
 
 static const struct drm_connector_funcs ast_vga_connector_funcs = {
@@ -1379,7 +1380,7 @@ static int ast_vga_connector_init(struct drm_device *dev, struct drm_connector *
 	connector->interlace_allowed = 0;
 	connector->doublescan_allowed = 0;
 
-	connector->polled = DRM_CONNECTOR_POLL_CONNECT;
+	connector->polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
 
 	return 0;
 }
@@ -1414,6 +1415,7 @@ static int ast_vga_output_init(struct ast_device *ast)
 
 static const struct drm_connector_helper_funcs ast_sil164_connector_helper_funcs = {
 	.get_modes = drm_connector_helper_get_modes,
+	.detect_ctx = drm_connector_helper_detect_ctx,
 };
 
 static const struct drm_connector_funcs ast_sil164_connector_funcs = {
@@ -1447,7 +1449,7 @@ static int ast_sil164_connector_init(struct drm_device *dev, struct drm_connecto
 	connector->interlace_allowed = 0;
 	connector->doublescan_allowed = 0;
 
-	connector->polled = DRM_CONNECTOR_POLL_CONNECT;
+	connector->polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
 
 	return 0;
 }
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 4d60cc810b577..b06dcc6c614e8 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -1272,3 +1272,32 @@ int drm_connector_helper_tv_get_modes(struct drm_connector *connector)
 	return i;
 }
 EXPORT_SYMBOL(drm_connector_helper_tv_get_modes);
+
+/**
+ * drm_connector_helper_detect_ctx - Read EDID and detect connector status.
+ * @connector: The connector
+ * @ctx: Acquire context
+ * @force: Perform screen-destructive operations, if necessary
+ *
+ * Detects the connector status by reading the EDID using drm_probe_ddc(),
+ * which requires connector->ddc to be set. Returns connector_status_connected
+ * on success or connector_status_disconnected on failure.
+ *
+ * Returns:
+ * The connector status as defined by enum drm_connector_status.
+ */
+int drm_connector_helper_detect_ctx(struct drm_connector *connector,
+				    struct drm_modeset_acquire_ctx *ctx,
+				    bool force)
+{
+	struct i2c_adapter *ddc = connector->ddc;
+
+	if (!ddc)
+		return connector_status_unknown;
+
+	if (drm_probe_ddc(ddc))
+		return connector_status_connected;
+
+	return connector_status_disconnected;
+}
+EXPORT_SYMBOL(drm_connector_helper_detect_ctx);
diff --git a/include/drm/drm_probe_helper.h b/include/drm/drm_probe_helper.h
index 62741a88796bb..031b044528c89 100644
--- a/include/drm/drm_probe_helper.h
+++ b/include/drm/drm_probe_helper.h
@@ -37,4 +37,7 @@ int drm_connector_helper_get_modes_fixed(struct drm_connector *connector,
 int drm_connector_helper_get_modes(struct drm_connector *connector);
 int drm_connector_helper_tv_get_modes(struct drm_connector *connector);
 
+int drm_connector_helper_detect_ctx(struct drm_connector *connector,
+				    struct drm_modeset_acquire_ctx *ctx,
+				    bool force);
 #endif
-- 
2.44.0