[PATCH v1] drm/vkms: Add writeback encoders as possible clones

[Robert Mader]

Since commit 41b4b11da0215 ("drm: Add valid clones check") setting
the `possible_clones` values is a hard requirement for cloning.
`vkms` supports cloning for writeback connectors in order to capture
CRTC content, however that broke with said commit.

Writeback connectors are created on a per-CRTC basis, thus mark
every non-writeback connector that is compatible with a given CRTC
as possible clone - and vice-versa.

Using a default configuration, the corresponding `drm_info` output
changes from:

├───Encoders
│   ├───Encoder 0
│   │   ├───Object ID: 40
│   │   ├───Type: virtual
│   │   ├───CRTCS: {0}
│   │   └───Clones: {0}
│   └───Encoder 1
│       ├───Object ID: 41
│       ├───Type: virtual
│       ├───CRTCS: {0}
│       └───Clones: {1}

to:

├───Encoders
│   ├───Encoder 0
│   │   ├───Object ID: 44
│   │   ├───Type: virtual
│   │   ├───CRTCS: {0}
│   │   └───Clones: {0, 1}
│   └───Encoder 1
│       ├───Object ID: 50
│       ├───Type: virtual
│       ├───CRTCS: {0}
│       └───Clones: {0, 1}

Signed-off-by: Robert Mader <robert.mader at collabora.com>
---
 drivers/gpu/drm/vkms/vkms_output.c    | 12 ++++++++++++
 drivers/gpu/drm/vkms/vkms_writeback.c |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
index 8d7ca0cdd79f..21935eb88198 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -77,9 +77,21 @@ int vkms_output_init(struct vkms_device *vkmsdev)
 			return ret;
 		}
 
+		encoder_cfg->encoder->possible_clones |= BIT(drm_encoder_index(encoder_cfg->encoder));
+
 		vkms_config_encoder_for_each_possible_crtc(encoder_cfg, idx, possible_crtc) {
 			encoder_cfg->encoder->possible_crtcs |=
 				drm_crtc_mask(&possible_crtc->crtc->crtc);
+
+			if (vkms_config_crtc_get_writeback(possible_crtc)) {
+				struct drm_encoder *wb_encoder =
+					&possible_crtc->crtc->wb_encoder;
+
+				encoder_cfg->encoder->possible_clones |=
+					BIT(drm_encoder_index(wb_encoder));
+				wb_encoder->possible_clones |=
+					BIT(drm_encoder_index(encoder_cfg->encoder));
+			}
 		}
 	}
 
diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c b/drivers/gpu/drm/vkms/vkms_writeback.c
index fe163271d5b5..12b60fb97c68 100644
--- a/drivers/gpu/drm/vkms/vkms_writeback.c
+++ b/drivers/gpu/drm/vkms/vkms_writeback.c
@@ -174,6 +174,8 @@ int vkms_enable_writeback_connector(struct vkms_device *vkmsdev,
 	if (ret)
 		return ret;
 	vkms_output->wb_encoder.possible_crtcs |= drm_crtc_mask(&vkms_output->crtc);
+	vkms_output->wb_encoder.possible_clones |=
+		BIT(drm_encoder_index(&vkms_output->wb_encoder));
 
 	drm_connector_helper_add(&wb->base, &vkms_wb_conn_helper_funcs);
 
-- 
2.50.0