RE: [PATCH] lib/igt_kms: Do not treat writeback and virtual connectors as connected

Hi @Mark Yacoub

> -----Original Message-----
> From: igt-dev <[email protected]> On Behalf Of Mark
> Yacoub
> Sent: 20 August 2026 00:38
> To: [email protected]
> Cc: Mark Yacoub <[email protected]>
> Subject: [PATCH] lib/igt_kms: Do not treat writeback and virtual connectors as
> connected
> 
> Writeback and virtual connectors (e.g. DRM_MODE_CONNECTOR_WRITEBACK
> and
> DRM_MODE_CONNECTOR_VIRTUAL) do not represent physical display sinks
> and cannot be modeset using standard CRTC / atomic commit operations
> without configuring a writeback output framebuffer (WRITEBACK_FB_ID).
> 
> On drivers such as MSM, writeback connectors (e.g. Virtual-1, Virtual-2) report
> connected status with virtual modes. When generic KMS tests iterate over
> connected outputs via for_each_connected_output() or during initial display
> setup in igt_display_init(), attempting standard modesets on these connectors
> causes failures (-EINVAL) before test execution can begin.
> 
> Exclude DRM_MODE_CONNECTOR_WRITEBACK and
> DRM_MODE_CONNECTOR_VIRTUAL in
> igt_output_is_connected() so generic KMS tests only target standard physical
> display outputs, while dedicated writeback tests can continue to iterate all
> outputs explicitly via for_each_output().
> 
> Signed-off-by: Mark Yacoub <[email protected]>
> ---
>  lib/igt_kms.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/lib/igt_kms.h b/lib/igt_kms.h index 521a03c01..8d4d14847 100644
> --- a/lib/igt_kms.h
> +++ b/lib/igt_kms.h
> @@ -668,6 +668,10 @@ static inline bool
> igt_output_is_connected(igt_output_t *output)
>  	    !output->config.connector->count_modes)
>  		return false;
> 
> +	if (output->config.connector->connector_type ==
> DRM_MODE_CONNECTOR_WRITEBACK ||
> +	    output->config.connector->connector_type ==
> DRM_MODE_CONNECTOR_VIRTUAL)
> +		return false;
> +
writeback tests already bypass igt_output_is_connected() by design and continue to work via for_each_output(), while generic tests correctly stop trying to modeset writeback/virtual connectors.
LGTM,
Reviewed-by: Sowmiya S <[email protected]>

>  	if (output->config.connector->connection ==
> DRM_MODE_CONNECTED)
>  		return true;
> 
> --
> 2.55.0.737.g08866a6d13-goog