mode: Retrieve only the current information for a Connector

Add a new API that allows the caller to skip any forced probing, which
may require slow i2c to a remote display, and only report the currently
active mode and encoder for a Connector. This is often the information
of interest and is much, much faster than re-retrieving the link status
and EDIDs, e.g. if the caller only wishes to count the number of active
outputs.

v2: Fix error path to avoid double free after a failed GETCONNECTOR
ioctl.

v3: Daniel strongly disapproved of my disjoint in behaviour between
GetConnector and GetConnectorCurrent, and considering how best to make a
drop in replacement for drmmode_output_init() convinced me keeping the
API as consistent as possible was the right approach.

v4: Avoid probing on the second calls to GETCONNECTOR for unconnected
outputs.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: David Herrmann <dh.herrmann@googlemail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 15 insertions, 2 deletions

diff --git a/xf86drmMode.h b/xf86drmMode.h
index 2d30184e..20c3f153 100644
--- a/xf86drmMode.h
+++ b/xf86drmMode.h
@@ -422,10 +422,23 @@ drmModeEncoderPtr drmModeGetEncoder(int fd, uint32_t encoder_id);
  */
 
 /**
- * Retrive information about the connector connectorId.
+ * Retrieve all information about the connector connectorId. This will do a
+ * forced probe on the connector to retrieve remote information such as EDIDs
+ * from the display device.
  */
 extern drmModeConnectorPtr drmModeGetConnector(int fd,
-                uint32_t connectorId);
+                                               uint32_t connectorId);
+
+/**
+ * Retrieve current information, i.e the currently active mode and encoder,
+ * about the connector connectorId. This will not do any probing on the
+ * connector or remote device, and only reports what is currently known.
+ * For the complete set of modes and encoders associated with the connector
+ * use drmModeGetConnector() which will do a probe to determine any display
+ * link changes first.
+ */
+extern drmModeConnectorPtr drmModeGetConnectorCurrent(int fd,
+                                                      uint32_t connector_id);
 
 /**
  * Attaches the given mode to an connector.