Re: [PATCH v10 3/3] drm: writeback: Add client capability for exposing writeback connectors

[Brian Starkey]

Hi Liviu,

On Tue, Jun 12, 2018 at 02:52:33PM +0100, Liviu Dudau wrote:
> Due to the fact that writeback connectors behave in a special way
> in DRM (they always report being disconnected) we might confuse some
> userspace. Add a client capability for writeback connectors that will
> filter them out for clients that don't understand the capability.
>
> Changelog:
> - only accept the capability if the client has already set the
> DRM_CLIENT_CAP_ATOMIC one.
>
> Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
> Cc: Brian Starkey <brian.starkey@xxxxxxx>
> Signed-off-by: Liviu Dudau <liviu.dudau@xxxxxxx>

LGTM,

Reviewed-by: Brian Starkey <brian.starkey@xxxxxxx>

Thanks,
-Brian

> ---
> drivers/gpu/drm/drm_ioctl.c       | 7 +++++++
> drivers/gpu/drm/drm_mode_config.c | 5 +++++
> include/drm/drm_file.h            | 7 +++++++
> include/uapi/drm/drm.h            | 9 +++++++++
> 4 files changed, 28 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 0d4cfb232576f..fe49fb0356b5a 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -334,6 +334,13 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
> 			return -EINVAL;
> 		file_priv->aspect_ratio_allowed = req->value;
> 		break;
> +	case DRM_CLIENT_CAP_WRITEBACK_CONNECTORS:
> +		if (!file_priv->atomic)
> +			return -EINVAL;
> +		if (req->value > 1)
> +			return -EINVAL;
> +		file_priv->writeback_connectors = req->value;
> +		break;
> 	default:
> 		return -EINVAL;
> 	}
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index e5c653357024d..21e353bd3948e 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -145,6 +145,11 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
> 	count = 0;
> 	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
> 	drm_for_each_connector_iter(connector, &conn_iter) {
> +		/* only expose writeback connectors if userspace understands them */
> +		if (!file_priv->writeback_connectors &&
> +		    (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK))
> +			continue;
> +
> 		if (drm_lease_held(file_priv, connector->base.id)) {
> 			if (count < card_res->count_connectors &&
> 			    put_user(connector->base.id, connector_id + count)) {
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index 027ac16da3d15..26485acc51d79 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -192,6 +192,13 @@ struct drm_file {
> 	 */
> 	unsigned aspect_ratio_allowed:1;
>
> +	/**
> +	 * @writeback_connectors:
> +	 *
> +	 * True if client understands writeback connectors
> +	 */
> +	unsigned writeback_connectors:1;
> +
> 	/**
> 	 * @is_master:
> 	 *
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index 9c660e1688abe..300f336633f28 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -687,6 +687,15 @@ struct drm_get_cap {
>  */
> #define DRM_CLIENT_CAP_ASPECT_RATIO    4
>
> +/**
> + * DRM_CLIENT_CAP_WRITEBACK_CONNECTORS
> + *
> + * If set to 1, the DRM core will expose special connectors to be used for
> + * writing back to memory the scene setup in the commit. Depends on client
> + * also supporting DRM_CLIENT_CAP_ATOMIC
> + */
> +#define DRM_CLIENT_CAP_WRITEBACK_CONNECTORS	5
> +
> /** DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
> struct drm_set_client_cap {
> 	__u64 capability;
> --
> 2.17.1