Re: [PATCH] drm/vkms: detect modes during output initialization

[Leandro Ribeiro <leandro.ribeiro@collabora.com>]

On 11/27/20 6:10 PM, Leandro Ribeiro wrote:
> In userspace we can use drmGetConnector() or drmGetConnectorCurrent() in
> order to retrieve connector information. The difference between both is
> that the former retrieves the complete set of modes and encoders
> associated with the connector, while the latter only retrieves the
> currently known set of modes and encoders - but is much faster.
> 
> This performance improvement is the reason why userspace applications
> may prefer to use drmGetConnectorCurrent() when they need to retrieve
> information from a device. The problem is that until now VKMS used to
> init its output with an encoder, but without any valid mode, so
> these userspace applications would not be able to use VKMS.
> 
> Call drm_helper_probe_single_connector_modes() during VKMS output
> initialization in order to start with the set of all valid modes.
> 
> Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
> ---
>  drivers/gpu/drm/vkms/vkms_output.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> index 4a1848b0318f..20343592d38a 100644
> --- a/drivers/gpu/drm/vkms/vkms_output.c
> +++ b/drivers/gpu/drm/vkms/vkms_output.c
> @@ -80,6 +80,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
>  		goto err_attach;
>  	}
>  
> +	ret = drm_helper_probe_single_connector_modes(connector, XRES_MAX, YRES_MAX);
> +	if (ret == 0) {
> +		DRM_ERROR("Failed to get modes for connector\n");
> +		goto err_attach;
> +	}
> +
>  	ret = vkms_enable_writeback_connector(vkmsdev);
>  	if (ret)
>  		DRM_ERROR("Failed to init writeback connector\n");
> 

After this patch we start to receive the warning from
drivers/gpu/drm/drm_modes.c:110

Thanks,
Leandro Ribeiro.
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