gamescope 0135: linear when the driver rejects every offered modifier

An r32p1 Mali-G610 (Vulkan 1.1) behind the Mali bridge answered both of the
backend's modifiers for AR24 with VK_ERROR_FORMAT_NOT_SUPPORTED, so the first
flippable image failed and gamescope asserted in vulkan_create_flat_texture
(Xiaomi 13T). Linear, when offered, is tried anyway; the bridge makes such
images without the handle type and exports them through a dma-heap. If the
image cannot be made, BInit fails as before.

tools/gamescope/PATCHES.md

@@ -122,6 +122,12 @@ app's Wayland-hosted gamescope never reaches, or need a newer gamescope than the
 - `0134-flippable-image-no-backend-modifiers.patch`: when the nested backend offers no modifier at all
   for a flippable image's format, `CVulkanTexture::BInit` tries linear and logs it instead of asserting
   `!modifiers.empty()`. NieR Replicant ended the session there on a Pixel 9a under Venus.
+- `0135-flippable-image-linear-when-driver-rejects-all.patch`: when the driver answers every offered
+  modifier with `VK_ERROR_FORMAT_NOT_SUPPORTED` and linear was among them, the flippable image tries
+  linear anyway; if it cannot be made, `BInit` fails as before. An r32p1 Mali-G610 (Vulkan 1.1) behind
+  the Mali bridge rejected both of the backend's modifiers for AR24, so the session ended at start
+  (0133's "no usable modifier"); the bridge makes such images without the handle type and exports
+  them through a dma-heap.
 
 The shared DroidDeck patch also includes `0116-release-cursor-shm-buffers.patch`: pointer cursor
 surfaces have no X11/xdg window association, so routing their commits through `g_PendingCommits`

tools/gamescope/patches/0135-flippable-image-linear-when-driver-rejects-all.patch

@@ -0,0 +1,38 @@
+--- a/src/rendervulkan.cpp
++++ b/src/rendervulkan.cpp
+@@ -2373,6 +2373,7 @@
+ 
+ 	std::vector<uint64_t> modifiers = {};
+ 	std::vector<uint64_t> unexportable = {};
++	bool linearRejected = false;
+ 	// TODO(JoshA): Move this code to backend for making flippable image.
+ 	if ( GetBackend()->UsesModifiers() && flags.bFlippable && g_device.supportsModifiers() && !pDMA )
+ 	{
+@@ -2414,7 +2415,10 @@
+ 			};
+ 			res = getModifierProps( &imageInfo, modifier, &externalFormatProps );
+ 			if ( res == VK_ERROR_FORMAT_NOT_SUPPORTED )
++			{
++				linearRejected |= modifier == DRM_FORMAT_MOD_LINEAR;
+ 				continue;
++			}
+ 			else if ( res != VK_SUCCESS ) {
+ 				vk_errorf( res, "getModifierProps failed" );
+ 				return false;
+@@ -2440,6 +2444,16 @@
+ 				drmFormat, unexportable.size() );
+ 			modifiers = unexportable;
+ 		}
++		// An r32p1 Mali driver (G610, Vulkan 1.1) behind the Mali bridge answers every modifier query
++		// with VK_ERROR_FORMAT_NOT_SUPPORTED, yet the bridge makes such an image without the handle type
++		// and exports it through a dma-heap. Linear, when the backend offered it, is tried rather than
++		// giving up; if the image cannot be made, BInit fails as before (Xiaomi 13T, AR24).
++		if ( modifiers.empty() && linearRejected )
++		{
++			vk_log.errorf( "flippable image: the driver supports none of the %zu modifier(s) offered for DRM format 0x%x; trying linear anyway",
++				numPossibleModifiers, drmFormat );
++			modifiers.push_back( DRM_FORMAT_MOD_LINEAR );
++		}
+ 		if ( modifiers.empty() )
+ 		{
+ 			vk_log.errorf( "flippable image: no usable modifier for DRM format 0x%x (%zu offered by the backend)", drmFormat, numPossibleModifiers );