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, 20 insertions, 3 deletions

diff --git a/xf86drmMode.c b/xf86drmMode.c
index 61d5e012..1333da48 100644
--- a/xf86drmMode.c
+++ b/xf86drmMode.c
@@ -476,19 +476,23 @@ drmModeEncoderPtr drmModeGetEncoder(int fd, uint32_t encoder_id)
 /*
  * Connector manipulation
  */
-
-drmModeConnectorPtr drmModeGetConnector(int fd, uint32_t connector_id)
+static drmModeConnectorPtr
+_drmModeGetConnector(int fd, uint32_t connector_id, int probe)
 {
 	struct drm_mode_get_connector conn, counts;
 	drmModeConnectorPtr r = NULL;
 
-retry:
 	memclear(conn);
 	conn.connector_id = connector_id;
+	if (!probe) {
+		conn.count_modes = 1;
+		conn.modes_ptr = VOID2U64(drmMalloc(sizeof(struct drm_mode_modeinfo)));
+	}
 
 	if (drmIoctl(fd, DRM_IOCTL_MODE_GETCONNECTOR, &conn))
 		return 0;
 
+retry:
 	counts = conn;
 
 	if (conn.count_props) {
@@ -504,6 +508,9 @@ retry:
 		conn.modes_ptr = VOID2U64(drmMalloc(conn.count_modes*sizeof(struct drm_mode_modeinfo)));
 		if (!conn.modes_ptr)
 			goto err_allocs;
+	} else {
+		conn.count_modes = 1;
+		conn.modes_ptr = VOID2U64(drmMalloc(sizeof(struct drm_mode_modeinfo)));
 	}
 
 	if (conn.count_encoders) {
@@ -572,6 +579,16 @@ err_allocs:
 	return r;
 }
 
+drmModeConnectorPtr drmModeGetConnector(int fd, uint32_t connector_id)
+{
+	return _drmModeGetConnector(fd, connector_id, 1);
+}
+
+drmModeConnectorPtr drmModeGetConnectorCurrent(int fd, uint32_t connector_id)
+{
+	return _drmModeGetConnector(fd, connector_id, 0);
+}
+
 int drmModeAttachMode(int fd, uint32_t connector_id, drmModeModeInfoPtr mode_info)
 {
 	struct drm_mode_mode_cmd res;