[PATCH i-g-t v2 2/5] lib/igt_kms: Add helper to wait for a specific status on a connector

[Kamil Konieczny]

Hi Louis,
On 2024-10-22 at 12:28:36 +0200, Louis Chauvet wrote:
> During testing with chamelium, it is frequent to wait for a specific
> connector status. This new helper is polling the DRM API to wait for this
> status. This allows detecting new status without notifier systems (which
> can fail if hot plug detection is not working properly on the device under
> test.
> 
> Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
> ---
>  lib/igt_kms.c | 38 ++++++++++++++++++++++++++++++++++++++
>  lib/igt_kms.h |  3 +++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
> index 195868646a14..40c0a207cd17 100644
> --- a/lib/igt_kms.c
> +++ b/lib/igt_kms.c
> @@ -7143,3 +7143,41 @@ float igt_default_detect_timeout(void)
>  
>  	return timeout;
>  }
> +
> +/**
> + * igt_wait_for_connector_status - Wait for at most @timeout that the connector @connector_id
> + * status become @drm_mode
> + *
> + * @drm_fd: drm file descriptor
> + * @connector_id: connector to monitor
> + * @timeout: maximum duration to wait, in second
> + * @drm_mode: mode to wait for, see enum drmModeConnection
> + *
> + * Returns: true when the status is reached, false if there is a timeout
> + */
> +bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double timeout,
> +				   int drm_mode)
> +{
> +	drmModeConnector *connector;
> +	struct timespec start, end;
> +
> +	if (timeout == 0.0)

Floating comparision is tricky, I would suggest something like
	if (abs(timeout) < epsilon)

> +		timeout = igt_default_detect_timeout();

What if it is still zero here?

Regards,
Kamil

> +
> +	clock_gettime(CLOCK_MONOTONIC, &start);
> +	clock_gettime(CLOCK_MONOTONIC, &end);
> +
> +	while (igt_time_elapsed(&start, &end) <= timeout) {
> +		connector = drmModeGetConnector(drm_fd, connector_id);
> +		if (connector && connector->connection == drm_mode) {
> +			free(connector);
> +			return true;
> +		}
> +		free(connector);
> +		clock_gettime(CLOCK_MONOTONIC, &end);
> +	}
> +
> +	igt_debug("Timeout waiting for connection status %d on connector %d\n", drm_mode,
> +		  connector_id);
> +	return false;
> +}
> diff --git a/lib/igt_kms.h b/lib/igt_kms.h
> index 4f0030264d9f..4cd4a4f65460 100644
> --- a/lib/igt_kms.h
> +++ b/lib/igt_kms.h
> @@ -1263,4 +1263,7 @@ void igt_reset_link_params(int drm_fd, igt_output_t *output);
>  
>  float igt_default_detect_timeout(void);
>  
> +bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double timeout,
> +				   int drm_mode);
> +
>  #endif /* __IGT_KMS_H__ */
> 
> -- 
> 2.46.2
>