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

From: Brian Starkey
Date: Wed Jun 13 2018 - 06:26:20 EST


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