From 9fc2d8e1fbc02cecc020e929e0dd2d408179d619 Mon Sep 17 00:00:00 2001
From: Ikalco <73481042+ikalco@users.noreply.github.com>
Date: Mon, 9 Dec 2024 15:14:39 -0600
Subject: [PATCH] drm: allow multigpu blit from explicit to implicit (#114)

---
 src/allocator/GBM.cpp        | 12 +++++++-----
 src/backend/drm/DRM.cpp      |  2 +-
 src/backend/drm/Renderer.cpp |  5 -----
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/allocator/GBM.cpp b/src/allocator/GBM.cpp
index 37dc3e0..02defff 100644
--- a/src/allocator/GBM.cpp
+++ b/src/allocator/GBM.cpp
@@ -103,12 +103,14 @@ Aquamarine::CGBMBuffer::CGBMBuffer(const SAllocatorBufferParams& params, Hypruti
         return;
     }
 
+    bool foundFormat = false;
     // check if we can use modifiers. If the requested support has any explicit modifier
     // supported by the primary backend, we can.
     for (auto const& f : FORMATS) {
         if (f.drmFormat != attrs.format)
             continue;
 
+        foundFormat = true;
         for (auto const& m : f.modifiers) {
             if (m == DRM_FORMAT_MOD_INVALID)
                 continue;
@@ -134,17 +136,17 @@ Aquamarine::CGBMBuffer::CGBMBuffer(const SAllocatorBufferParams& params, Hypruti
         }
     }
 
+    if (!foundFormat) {
+        allocator->backend->log(AQ_LOG_ERROR, std::format("GBM: Failed to allocate a GBM buffer: format {} isn't supported by primary backend", fourccToName(attrs.format)));
+        return;
+    }
+
     // FIXME: Nvidia cannot render to linear buffers. What do?
     if (MULTIGPU) {
         allocator->backend->log(AQ_LOG_DEBUG, "GBM: Buffer is marked as multigpu, forcing linear");
         explicitModifiers = {DRM_FORMAT_MOD_LINEAR};
     }
 
-    if (explicitModifiers.empty()) {
-        // fall back to using a linear buffer.
-        explicitModifiers.push_back(DRM_FORMAT_MOD_LINEAR);
-    }
-
     uint32_t flags = GBM_BO_USE_RENDERING;
     if (params.scanout)
         flags |= GBM_BO_USE_SCANOUT;
diff --git a/src/backend/drm/DRM.cpp b/src/backend/drm/DRM.cpp
index 38d1df8..f39d382 100644
--- a/src/backend/drm/DRM.cpp
+++ b/src/backend/drm/DRM.cpp
@@ -527,7 +527,7 @@ void Aquamarine::CDRMBackend::buildGlFormats(const std::vector<SGLFormat>& fmts)
     std::vector<SDRMFormat> result;
 
     for (auto const& fmt : fmts) {
-        if (fmt.external)
+        if (fmt.external && fmt.modifier != DRM_FORMAT_MOD_INVALID)
             continue;
 
         if (auto it = std::find_if(result.begin(), result.end(), [fmt](const auto& e) { return fmt.drmFormat == e.drmFormat; }); it != result.end()) {
diff --git a/src/backend/drm/Renderer.cpp b/src/backend/drm/Renderer.cpp
index 896f593..a1683d8 100644
--- a/src/backend/drm/Renderer.cpp
+++ b/src/backend/drm/Renderer.cpp
@@ -809,11 +809,6 @@ bool CDRMRenderer::verifyDestinationDMABUF(const SDMABUFAttrs& attrs) {
         if (fmt.modifier != attrs.modifier)
             continue;
 
-        if (fmt.external) {
-            backend->log(AQ_LOG_ERROR, "EGL (verifyDestinationDMABUF): FAIL, format is external-only");
-            return false;
-        }
-
         return true;
     }