The Media controller doesn't tell much to the user in cases such as pipeline startup failure. The link validation is the most common media graph (or in V4L2's case, format) related reason for the failure. In more complex pipelines the reason may not always be obvious to the user, so point them to look at the right direction.
Unified · Split
| @@ -279,8 +279,14 @@ __must_check int media_entity_pipeline_start(struct media_entity *entity, · 278 unmodified lines | ||
| 279 | 279 | continue; |
| 280 | 280 | |
| 281 | 281 | ret = entity->ops->link_validate(link); |
| 282 | − if (ret < 0 && ret != -ENOIOCTLCMD) | |
| 282 | + if (ret < 0 && ret != -ENOIOCTLCMD) { | |
| 283 | + dev_dbg(entity->parent->dev, | |
| 284 | + "link validation failed for \"%s\":%u -> \"%s\":%u, error %d\n", | |
| 285 | + entity->name, link->source->index, | |
| 286 | + link->sink->entity->name, | |
| 287 | + link->sink->index, ret); | |
| 283 | 288 | goto error; |
| 289 | + } | |
| 284 | 290 | } |
| 285 | 291 | |
| 286 | 292 | /* Either no links or validated links are fine. */ |
| @@ -288,6 +294,10 @@ __must_check int media_entity_pipeline_start(struct media_entity *entity, · 1 unmodified line | ||
| 288 | 294 | |
| 289 | 295 | if (!bitmap_full(active, entity->num_pads)) { |
| 290 | 296 | ret = -EPIPE; |
| 297 | + dev_dbg(entity->parent->dev, | |
| 298 | + "\"%s\":%u must be connected by an enabled link\n", | |
| 299 | + entity->name, | |
| 300 | + find_first_zero_bit(active, entity->num_pads)); | |
| 291 | 301 | goto error; |
| 292 | 302 | } |
| 293 | 303 | } |