[PATCH i-g-t v2 3/5] lib/igt_kms: Add function to list connected connectors

[Kamil Konieczny]

Hi Louis,
On 2024-10-22 at 12:28:37 +0200, Louis Chauvet wrote:
> Introduce the igt_get_connected_connectors() function, which returns a
> list of connector IDs that are currently connected according to DRM.
> 
> This function includes a timeout mechanism because connectors can be
> unplugged at any time. Also, especially with MST, the connector can be
> listed by drmModeGetResources() but not yet accessible with
> drmModeGetConnector().
> 
> Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
> ---
>  lib/igt_kms.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/igt_kms.h |  1 +
>  2 files changed, 55 insertions(+)
> 
> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
> index 40c0a207cd17..44b546ae52dc 100644
> --- a/lib/igt_kms.c
> +++ b/lib/igt_kms.c
> @@ -7181,3 +7181,57 @@ bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double
>  		  connector_id);
>  	return false;
>  }
> +
> +/**
> + * igt_get_connected_connectors - List all connectors reported as CONNECTED by DRM.
> + *
> + * @drm_fd: DRM file description
> + * @connector_ids: out pointer for the list of connector ids connected. It must be freed by the
> + * caller.
> + *
> + * The returns value is the number of connectors
> + */
> +int igt_get_connected_connectors(int drm_fd, uint32_t **connector_ids)
> +{
> +	int connected_count = 0;
> +	drmModeResPtr resources;
> +	struct timespec start, end;
> +
> +	*connector_ids = NULL;
> +
> +	resources = drmModeGetResources(drm_fd);
> +	for (int j = 0; j < resources->count_connectors; j++) {
> +		drmModeConnectorPtr connector = NULL;
> +
> +		connector = drmModeGetConnector(drm_fd, resources->connectors[j]);
> +		/*
> +		 * This time is required as sometimes some id in the connector list are not totally
> +		 * ready or can disappear
> +		 */
> +		clock_gettime(CLOCK_MONOTONIC, &start);
> +		clock_gettime(CLOCK_MONOTONIC, &end);
> +		while (!connector &&
> +		       igt_time_elapsed(&start, &end) < igt_default_detect_timeout()) {
> +			connector = drmModeGetConnector(drm_fd, resources->connectors[j]);
> +			clock_gettime(CLOCK_MONOTONIC, &end);
> +		}
> +
> +		if (igt_time_elapsed(&start, &end) < igt_default_detect_timeout()) {
> +			igt_assert(connector);

Please try to not assert in lib functions, unless abslutly nessesery.
Why not just return zero in case no connected connectors are detected.

Regards,
Kamil

> +
> +			if (connector->connection == DRM_MODE_CONNECTED) {
> +				*connector_ids = reallocarray(*connector_ids,
> +							      connected_count
> +							      + 1, sizeof(**connector_ids));
> +				igt_assert(*connector_ids);
> +				(*connector_ids)[connected_count] = resources->connectors[j];
> +				connected_count++;
> +			}
> +			drmModeFreeConnector(connector);
> +		}
> +	}
> +	drmModeFreeResources(resources);
> +
> +	return
> +	    connected_count;
> +}
> diff --git a/lib/igt_kms.h b/lib/igt_kms.h
> index 4cd4a4f65460..4674b271638a 100644
> --- a/lib/igt_kms.h
> +++ b/lib/igt_kms.h
> @@ -1265,5 +1265,6 @@ float igt_default_detect_timeout(void);
>  
>  bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double timeout,
>  				   int drm_mode);
> +int igt_get_connected_connectors(int drm_fd, uint32_t **connector_ids);
>  
>  #endif /* __IGT_KMS_H__ */
> 
> -- 
> 2.46.2
>