[plasma/kwin] /: wayland: implement linux dmabuf version 6

Xaver Hugl <[email protected]>
Newsgroups gmane.comp.kde.cvs
Message-ID <[email protected]> 
Git commit e0cce2fd1f62f6a01e714f4212ce03fee2b2a8f0 by Xaver Hugl.
Committed on 28/07/2026 at 10:59.
Pushed by zamundaaa into branch 'master'.

wayland: implement linux dmabuf version 6

This ports the protocol to version 6, but there are no functional changes yet.

M  +1    -1    CMakeLists.txt
M  +1    -1    src/wayland-client/linuxdmabuf.cpp
M  +33   -20   src/wayland/linuxdmabufv1clientbuffer.cpp
M  +2    -0    src/wayland/linuxdmabufv1clientbuffer_p.h

https://invent.kde.org/plasma/kwin/-/commit/e0cce2fd1f62f6a01e714f4212ce03fee2b2a8f0

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8788c3f14e4..6d77a57976e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -211,7 +211,7 @@ if (Wayland_VERSION VERSION_GREATER_EQUAL "1.25.91")
     add_compile_definitions(HAVE_ACK_GLOBAL_REMOVE=1)
 endif()
 
-find_package(WaylandProtocols 1.48)
+find_package(WaylandProtocols 1.49)
 set_package_properties(WaylandProtocols PROPERTIES
     TYPE REQUIRED
     PURPOSE "Collection of Wayland protocols that add functionality not available in the Wayland core protocol"
diff --git a/src/wayland-client/linuxdmabuf.cpp b/src/wayland-client/linuxdmabuf.cpp
index 17d3d4e4b68..5b323f68be0 100644
--- a/src/wayland-client/linuxdmabuf.cpp
+++ b/src/wayland-client/linuxdmabuf.cpp
@@ -135,7 +135,7 @@ void LinuxDmabufFeedbackV1::tranche_flags(void *data, zwp_linux_dmabuf_feedback_
 
 LinuxDmabufV1::LinuxDmabufV1(wl_registry *registry, uint32_t name, uint32_t version)
 {
-    m_dmabuf = static_cast<zwp_linux_dmabuf_v1 *>(wl_registry_bind(registry, name, &zwp_linux_dmabuf_v1_interface, version));
+    m_dmabuf = static_cast<zwp_linux_dmabuf_v1 *>(wl_registry_bind(registry, name, &zwp_linux_dmabuf_v1_interface, std::min(4u, version)));
 
     static const struct zwp_linux_dmabuf_v1_listener dmabufListener = {
         .format = format,
diff --git a/src/wayland/linuxdmabufv1clientbuffer.cpp b/src/wayland/linuxdmabufv1clientbuffer.cpp
index 8e5bab213f1..ae4935e8106 100644
--- a/src/wayland/linuxdmabufv1clientbuffer.cpp
+++ b/src/wayland/linuxdmabufv1clientbuffer.cpp
@@ -28,7 +28,7 @@
 namespace KWin
 {
 
-static const int s_version = 5;
+static const int s_version = 6;
 
 LinuxDmaBufV1ClientBufferIntegrationPrivate::LinuxDmaBufV1ClientBufferIntegrationPrivate(LinuxDmaBufV1ClientBufferIntegration *q, Display *display)
     : QtWaylandServer::zwp_linux_dmabuf_v1(*display, s_version)
@@ -103,7 +103,9 @@ LinuxDmaBufParamsV1::LinuxDmaBufParamsV1(LinuxDmaBufV1ClientBufferIntegration *i
     : QtWaylandServer::zwp_linux_buffer_params_v1(resource)
     , m_integration(integration)
 {
-    m_attrs.device = integration->mainDevice(wl_resource_get_client(resource));
+    if (wl_resource_get_version(resource) < ZWP_LINUX_BUFFER_PARAMS_V1_SET_SAMPLING_DEVICE_SINCE_VERSION) {
+        m_targetDevice = integration->mainDevice(wl_resource_get_client(resource));
+    }
 }
 
 void LinuxDmaBufParamsV1::zwp_linux_buffer_params_v1_destroy_resource(Resource *resource)
@@ -174,6 +176,7 @@ void LinuxDmaBufParamsV1::zwp_linux_buffer_params_v1_create(Resource *resource,
     m_attrs.width = width;
     m_attrs.height = height;
     m_attrs.format = format;
+    m_attrs.device = m_targetDevice.value_or(m_integration->mainDevice(resource->client()));
 
     auto clientBuffer = new LinuxDmaBufV1ClientBuffer(std::move(m_attrs));
     if (!renderBackend->testImportBuffer(clientBuffer)) {
@@ -225,6 +228,7 @@ void LinuxDmaBufParamsV1::zwp_linux_buffer_params_v1_create_immed(Resource *reso
     m_attrs.width = width;
     m_attrs.height = height;
     m_attrs.format = format;
+    m_attrs.device = m_targetDevice.value_or(m_integration->mainDevice(resource->client()));
 
     auto clientBuffer = new LinuxDmaBufV1ClientBuffer(std::move(m_attrs));
     if (!renderBackend->testImportBuffer(clientBuffer)) {
@@ -243,6 +247,15 @@ void LinuxDmaBufParamsV1::zwp_linux_buffer_params_v1_create_immed(Resource *reso
     clientBuffer->initialize(bufferResource);
 }
 
+void LinuxDmaBufParamsV1::zwp_linux_buffer_params_v1_set_sampling_device(Resource *resource, wl_array *device)
+{
+    if (device->size < sizeof(dev_t)) {
+        wl_resource_post_error(resource->handle, error_invalid_dev_t_size, "Incomplete dev_t sent!");
+        return;
+    }
+    m_targetDevice = *reinterpret_cast<dev_t *>(device->data);
+}
+
 bool LinuxDmaBufParamsV1::test(Resource *resource, uint32_t width, uint32_t height)
 {
     if (Q_UNLIKELY(!m_attrs.planeCount)) {
@@ -461,17 +474,7 @@ QList<LinuxDmaBufV1Feedback::Tranche> LinuxDmaBufV1Feedback::createScanoutTranch
     if (!scanoutDevice) {
         return ret;
     }
-    RenderDevice *compatibleWithScanout = GpuManager::self()->compatibleRenderDevice(scanoutDevice);
     for (const auto &tranche : tranches) {
-        // for now, limit scanout tranches to the main device
-        // TODO relax this with dmabuf v6
-        if (tranche.device != mainDevice) {
-            continue;
-        }
-        if (compatibleWithScanout && tranche.device != compatibleWithScanout->deviceId()) {
-            // limit scanout tranches to devices we can also sample from
-            continue;
-        }
         LinuxDmaBufV1Feedback::Tranche scanoutTranche;
         for (auto it = tranche.formatTable.constBegin(); it != tranche.formatTable.constEnd(); it++) {
             const uint32_t format = it.key();
@@ -485,7 +488,7 @@ QList<LinuxDmaBufV1Feedback::Tranche> LinuxDmaBufV1Feedback::createScanoutTranch
         }
         if (!scanoutTranche.formatTable.isEmpty()) {
             scanoutTranche.device = scanoutDevice->deviceId();
-            scanoutTranche.flags = tranche.flags | LinuxDmaBufV1Feedback::TrancheFlag::Scanout;
+            scanoutTranche.flags = LinuxDmaBufV1Feedback::TrancheFlag::Scanout;
             ret.push_back(scanoutTranche);
         }
     }
@@ -507,10 +510,19 @@ void LinuxDmaBufV1FeedbackPrivate::send(Resource *resource)
 {
     const dev_t mainDevice = m_bufferintegration->q->mainDevice(resource->client());
     send_format_table(resource->handle, m_bufferintegration->table->file.fd(), m_bufferintegration->table->file.size());
-    QByteArray bytes;
-    bytes.append(reinterpret_cast<const char *>(&mainDevice), sizeof(dev_t));
-    send_main_device(resource->handle, bytes);
-    const auto sendTranche = [this, resource](const LinuxDmaBufV1Feedback::Tranche &tranche) {
+    if (resource->version() < ZWP_LINUX_BUFFER_PARAMS_V1_SET_SAMPLING_DEVICE_SINCE_VERSION) {
+        QByteArray bytes;
+        bytes.append(reinterpret_cast<const char *>(&mainDevice), sizeof(dev_t));
+        send_main_device(resource->handle, bytes);
+    }
+    const auto sendTranche = [this, resource, mainDevice](const LinuxDmaBufV1Feedback::Tranche &tranche) {
+        const bool supportsSamplingFlag = resource->version() >= ZWP_LINUX_DMABUF_FEEDBACK_V1_TRANCHE_FLAGS_SAMPLING_SINCE_VERSION;
+        if (!supportsSamplingFlag
+            && tranche.flags == LinuxDmaBufV1Feedback::TrancheFlag::Sampling
+            && tranche.device != mainDevice) {
+            // dmabuf v5 only supports the main device for sampling
+            return;
+        }
         QByteArray targetDevice;
         targetDevice.append(reinterpret_cast<const char *>(&tranche.device), sizeof(dev_t));
         QByteArray indices;
@@ -527,6 +539,10 @@ void LinuxDmaBufV1FeedbackPrivate::send(Resource *resource)
         if (tranche.flags & LinuxDmaBufV1Feedback::TrancheFlag::Scanout) {
             flags |= tranche_flags_scanout;
         }
+        if (resource->version() >= ZWP_LINUX_BUFFER_PARAMS_V1_SET_SAMPLING_DEVICE_SINCE_VERSION
+            && (tranche.flags & LinuxDmaBufV1Feedback::TrancheFlag::Sampling)) {
+            flags |= tranche_flags_sampling;
+        }
         send_tranche_flags(resource->handle, flags);
         send_tranche_done(resource->handle);
     };
@@ -534,9 +550,6 @@ void LinuxDmaBufV1FeedbackPrivate::send(Resource *resource)
         sendTranche(tranche);
     }
     for (const auto &tranche : std::as_const(m_bufferintegration->defaultTranches)) {
-        if (tranche.device != mainDevice) {
-            continue;
-        }
         sendTranche(tranche);
     }
     send_done(resource->handle);
diff --git a/src/wayland/linuxdmabufv1clientbuffer_p.h b/src/wayland/linuxdmabufv1clientbuffer_p.h
index 7fc4fcae955..c3efedfa2e2 100644
--- a/src/wayland/linuxdmabufv1clientbuffer_p.h
+++ b/src/wayland/linuxdmabufv1clientbuffer_p.h
@@ -70,6 +70,7 @@ protected:
     void zwp_linux_buffer_params_v1_create(Resource *resource, int32_t width, int32_t height, uint32_t format, uint32_t flags) override;
     void
     zwp_linux_buffer_params_v1_create_immed(Resource *resource, uint32_t buffer_id, int32_t width, int32_t height, uint32_t format, uint32_t flags) override;
+    void zwp_linux_buffer_params_v1_set_sampling_device(Resource *resource, wl_array *device) override;
 
 private:
     bool test(Resource *resource, uint32_t width, uint32_t height);
@@ -77,6 +78,7 @@ private:
     LinuxDmaBufV1ClientBufferIntegration *m_integration;
     DmaBufAttributes m_attrs;
     std::array<uint64_t, 4> m_modifiers;
+    std::optional<dev_t> m_targetDevice;
     bool m_isUsed = false;
 };
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