hw/display: Allow injection of virtio-gpu EDID name

Thanks to 72d277a7, 1ed2cb32, and others, EDID (Extended Display
Identification Data) is propagated by QEMU such that a virtual display
presents legitimate metadata (e.g., name, serial number, preferred
resolutions, etc.) to its connected guest.

This change adds the ability to specify the EDID name for a particular
virtio-vga display. Previously, every virtual display would have the same
name: "QEMU Monitor". Now, we can inject names of displays in order to test
guest behavior that is specific to display names. We provide the ability to
inject the display name from the frontend since this is guest visible
data. Furthermore, this makes it clear where N potential display outputs
would get their name from (which will be added in a future change).

Note that we have elected to use a struct here for output data for
extensibility - we intend to add per-output fields like resolution in a
future change.

It should be noted that EDID names longer than 12 bytes will be truncated
per spec (I think?).

Testing: verified that when I specified 2 outputs for a virtio-gpu with
edid_name set, the names matched those that I configured with my vnc
display.

  -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"
              },
              {
                 "name":"BBB"
              }
            ]}'

Signed-off-by: Andrew Keesler <ankeesler@google.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20250709121126.2946088-2-ankeesler@google.com>

3 files changed, 10 insertions, 0 deletions

diff --git a/include/hw/display/edid.h b/include/hw/display/edid.h
index 520f8ec..91c0a42 100644
--- a/include/hw/display/edid.h
+++ b/include/hw/display/edid.h
@@ -1,6 +1,8 @@
 #ifndef EDID_H
 #define EDID_H
 
+#define EDID_NAME_MAX_LENGTH 12
+
 typedef struct qemu_edid_info {
     const char *vendor; /* http://www.uefi.org/pnp_id_list */
     const char *name;
diff --git a/include/hw/qdev-properties-system.h b/include/hw/qdev-properties-system.h
index b921392..9601a11 100644
--- a/include/hw/qdev-properties-system.h
+++ b/include/hw/qdev-properties-system.h
@@ -32,6 +32,7 @@ extern const PropertyInfo qdev_prop_cpus390entitlement;
 extern const PropertyInfo qdev_prop_iothread_vq_mapping_list;
 extern const PropertyInfo qdev_prop_endian_mode;
 extern const PropertyInfo qdev_prop_vmapple_virtio_blk_variant;
+extern const PropertyInfo qdev_prop_virtio_gpu_output_list;
 
 #define DEFINE_PROP_PCI_DEVFN(_n, _s, _f, _d)                   \
     DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_pci_devfn, int32_t)
@@ -110,4 +111,8 @@ extern const PropertyInfo qdev_prop_vmapple_virtio_blk_variant;
                          qdev_prop_vmapple_virtio_blk_variant, \
                          VMAppleVirtioBlkVariant)
 
+#define DEFINE_PROP_VIRTIO_GPU_OUTPUT_LIST(_name, _state, _field) \
+    DEFINE_PROP(_name, _state, _field, qdev_prop_virtio_gpu_output_list, \
+                VirtIOGPUOutputList *)
+
 #endif
diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
index a42957c..9f16f89 100644
--- a/include/hw/virtio/virtio-gpu.h
+++ b/include/hw/virtio/virtio-gpu.h
@@ -20,6 +20,7 @@
 #include "hw/virtio/virtio.h"
 #include "qemu/log.h"
 #include "system/vhost-user-backend.h"
+#include "qapi/qapi-types-virtio.h"
 
 #include "standard-headers/linux/virtio_gpu.h"
 #include "standard-headers/linux/virtio_ids.h"
@@ -128,6 +129,7 @@ struct virtio_gpu_base_conf {
     uint32_t xres;
     uint32_t yres;
     uint64_t hostmem;
+    VirtIOGPUOutputList *outputs;
 };
 
 struct virtio_gpu_ctrl_command {
@@ -167,6 +169,7 @@ struct VirtIOGPUBaseClass {
 
 #define VIRTIO_GPU_BASE_PROPERTIES(_state, _conf)                       \
     DEFINE_PROP_UINT32("max_outputs", _state, _conf.max_outputs, 1),    \
+    DEFINE_PROP_VIRTIO_GPU_OUTPUT_LIST("outputs", _state, _conf.outputs), \
     DEFINE_PROP_BIT("edid", _state, _conf.flags, \
                     VIRTIO_GPU_FLAG_EDID_ENABLED, true), \
     DEFINE_PROP_UINT32("xres", _state, _conf.xres, 1280), \