[PATCH v2] 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}

Fixes: dbd9d80c1b2e (drm/vkms: Add support for writeback)
Signed-off-by: Robert Mader <robert.ma...@collabora.com>
---
 drivers/gpu/drm/vkms/vkms_output.c    | 13 +++++++++++++
 drivers/gpu/drm/vkms/vkms_writeback.c |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/vkms/vkms_output.c 
b/drivers/gpu/drm/vkms/vkms_output.c
index 8d7ca0cdd79f..2ee3749e2b28 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -77,9 +77,22 @@ int vkms_output_init(struct vkms_device *vkmsdev)
                        return ret;
                }
 
+               encoder_cfg->encoder->possible_clones |=
+                       drm_encoder_mask(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 |=
+                                       drm_encoder_mask(wb_encoder);
+                               wb_encoder->possible_clones |=
+                                       drm_encoder_mask(encoder_cfg->encoder);
+                       }
                }
        }
 
diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c 
b/drivers/gpu/drm/vkms/vkms_writeback.c
index fe163271d5b5..45d69a3b85f6 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 |=
+               drm_encoder_mask(&vkms_output->wb_encoder);
 
        drm_connector_helper_add(&wb->base, &vkms_wb_conn_helper_funcs);
 
-- 
2.50.1