kmscube.c: init_drm(): handle usecase where display is disabled

In some usecases HDMI is connected but is disabled by default.
In such scenario, connector->encoder_id and encoder->crtc_id
may be 0. This patch iterates over all possible encoders and
CRTCs to find and store the encoder and CRTC accordingly.

Signed-off-by: Eric Ruei <e-ruei1@ti.com>

1 files changed, 36 insertions, 5 deletions

diff --git a/kmscube.c b/kmscube.c
index 6bfa86a..9dbefa3 100644
--- a/kmscube.c
+++ b/kmscube.c
@@ -91,7 +91,7 @@ static int init_drm(void)
         drmModeEncoder *encoder = NULL;
         drmModeCrtc *crtc = NULL;
 
-        int i, j;
+        int i, j, k;
         uint32_t maxRes, curRes;
 
         for (i = 0; i < ARRAY_SIZE(modules); i++) {
@@ -123,18 +123,49 @@ static int init_drm(void)
                 if (connector->connection == DRM_MODE_CONNECTED) {
 
                         /* find the matched encoders */
-                        for (j=0; j<resources->count_encoders; j++) {
-                                encoder = drmModeGetEncoder(drm.fd, resources->encoders[j]);
+                        for (j=0; j<connector->count_encoders; j++) {
+                                encoder = drmModeGetEncoder(drm.fd, connector->encoders[j]);
+
+                                /* Take the fisrt one, if none is assigned */
+                                if (!connector->encoder_id)
+                                {
+                                        connector->encoder_id = encoder->encoder_id;
+                                }
+
                                 if (encoder->encoder_id == connector->encoder_id)
+                                {
+                                        /* find the first valid CRTC if not assigned */
+                                        if (!encoder->crtc_id)
+                                        {
+                                                for (k = 0; k < resources->count_crtcs; ++k) {
+                                                        /* check whether this CRTC works with the encoder */
+                                                        if (!(encoder->possible_crtcs & (1 << k)))
+                                                                continue;
+
+                                                        encoder->crtc_id = resources->crtcs[k];
+                                                        break;
+                                                }
+
+                                                if (!encoder->crtc_id)
+                                                {
+                                                        printf("Encoder(%d): no CRTC find!\n", encoder->encoder_id);
+                                                        drmModeFreeEncoder(encoder);
+                                                        encoder = NULL;
+                                                        continue;
+                                                }
+                                        }
+
                                         break;
+                                }
 
                                 drmModeFreeEncoder(encoder);
                                 encoder = NULL;
                         }
 
                         if (!encoder) {
-                                printf("no encoder!\n");
-                                return -1;
+                                printf("Connector (%d): no encoder!\n", connector->connector_id);
+                                drmModeFreeConnector(connector);
+                                continue;
                         }
 
                         /* choose the current or first supported mode */