[PATCH 1/8] Support per-head resolutions with virtio-gpu

["Alex Bennée" <alex.bennee@linaro.org>]

From: Andrew Keesler <ankeesler@google.com>

In 454f4b0f, we started down the path of supporting separate
configurations per display head (e.g., you have 2 heads - one with
EDID name "AAA" and the other with EDID name "BBB").

In this change, we add resolution to this configuration surface (e.g.,
you have 2 heads - one with resolution 111x222 and the other with
resolution 333x444).

  -display vnc=localhost:0,id=aaa,display=vga,head=0 \
  -display vnc=localhost:1,id=bbb,display=vga,head=1 \
  -device '{"driver":"virtio-vga",
            "max_outputs":2,
            "id":"vga",
            "outputs":[
              {
                 "name":"AAA",
                 "xres":111,
                 "yres":222
              },
              {
                 "name":"BBB",
                 "xres":333,
                 "yres":444
              }
            ]}'

Here is the behavior matrix of the current resolution configuration
surface (xres/yres) with the new resolution configuration surface
(outputs[i].xres/yres).

Case: !(xres || yres) && !(outputs[i].has_xres && outputs[i].has_yres)
Behavior: current behavior - outputs[0] enabled with default xres/yres

Case: (xres || yres) && !(outputs[i].has_xres && outputs[i].has_yres)
Behavior: current behavior - outputs[0] enabled with xres/yres

Case: !(xres || yres) && (outputs[i].has_xres && outputs[i].has_yres)
Behavior: new behavior - outputs[i] enabled with outputs[i].xres/yres

Case: (xres || yres) && (outputs[i].has_xres && outputs[i].has_yres)
Behavior: new behavior - outputs[i] enabled with outputs[i].xres/yres
Signed-off-by: Andrew Keesler <ankeesler@google.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250902141312.750525-2-ankeesler@google.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 qapi/virtio.json             | 10 ++++++++--
 hw/display/virtio-gpu-base.c | 10 ++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/qapi/virtio.json b/qapi/virtio.json
index 05295ab6655..0ce789bb22f 100644
--- a/qapi/virtio.json
+++ b/qapi/virtio.json
@@ -971,15 +971,21 @@
 ##
 # @VirtIOGPUOutput:
 #
-# Describes configuration of a VirtIO GPU output.
+# Describes configuration of a VirtIO GPU output. If both xres and
+# yres are set, they take precedence over root virtio-gpu
+# resolution configuration and enable the corresponding output.
 #
 # @name: the name of the output
 #
+# @xres: horizontal resolution of the output in pixels (since 10.2)
+#
+# @yres: vertical resolution of the output in pixels (since 10.2)
+#
 # Since: 10.1
 ##
 
 { 'struct': 'VirtIOGPUOutput',
-  'data': { 'name': 'str' } }
+  'data': { 'name': 'str', '*xres': 'uint16', '*yres': 'uint16' } }
 
 ##
 # @DummyVirtioForceArrays:
diff --git a/hw/display/virtio-gpu-base.c b/hw/display/virtio-gpu-base.c
index 7269477a1c8..6adb5312a40 100644
--- a/hw/display/virtio-gpu-base.c
+++ b/hw/display/virtio-gpu-base.c
@@ -233,6 +233,16 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
     g->req_state[0].width = g->conf.xres;
     g->req_state[0].height = g->conf.yres;
 
+    for (output_idx = 0, node = g->conf.outputs;
+         node && output_idx < g->conf.max_outputs;
+         output_idx++, node = node->next) {
+        if (node->value->has_xres && node->value->has_yres) {
+            g->enabled_output_bitmask |= (1 << output_idx);
+            g->req_state[output_idx].width = node->value->xres;
+            g->req_state[output_idx].height = node->value->yres;
+        }
+    }
+
     g->hw_ops = &virtio_gpu_ops;
     for (i = 0; i < g->conf.max_outputs; i++) {
         g->scanout[i].con =
-- 
2.47.3