amdgpu: resolve idr_* conflict with linux-kpi via REDBEAR_AMDGPU_BUILD

The linux-kpi idr.h header and the amdgpu recipe's redox_glue.h
both define struct idr and the idr_init/alloc/remove/find/destroy
inline functions, but with different members and different argument
signatures. When the amdgpu build includes both headers in the same
translation unit (via -include linux/amdgpu_stubs.h and via
redox_glue.h), the compiler reports a redefinition of struct idr
and conflicting types for the idr_* inlines, blocking the build.

Resolve the conflict by gating the linux-kpi idr declarations on a
new REDBEAR_AMDGPU_BUILD preprocessor flag. The amdgpu recipe's
CFLAGS now defines REDBEAR_AMDGPU_BUILD, so the linux-kpi
declarations are suppressed and redox_glue.h's authoritative copies
take over. Every other consumer of linux-kpi (the redox-drm scheme
daemon, the Wi-Fi drivers) continues to see the generic stubs.

The IDA macros and struct ida in linux-kpi are kept outside the
gate because they are not part of the amdgpu surface and must
remain available to other drivers. A forward declaration of
struct idr is added at the top of the header so the
struct ida { struct idr *idr; } member compiles cleanly when the
IDR definitions are suppressed. The IDA macros are updated to
no-ops against a pointer-typed idr slot; the amdgpu build does
not exercise them and other consumers continue to treat them as
stubs.

local/recipes/drivers/linux-kpi/source/src/c_headers/linux/idr.h

@@ -3,6 +3,24 @@
 
 #include <linux/types.h>
 
+/*
+ * The amdgpu recipe's redox_glue.h provides its own `struct idr`,
+ * `idr_init/alloc/remove/find/destroy`, `DEFINE_IDR`, and
+ * `idr_for_each_entry` declarations. To avoid the conflicting
+ * declarations when amdgpu and the linux-kpi headers are included
+ * in the same translation unit, the linux-kpi idr declarations are
+ * suppressed when REDBEAR_AMDGPU_BUILD is defined. The amdgpu
+ * recipe sets -DREDBEAR_AMDGPU_BUILD in its CFLAGS; every other
+ * consumer of linux-kpi keeps the generic stubs below.
+ *
+ * The IDA macros, `struct ida`, and the forward declaration of
+ * `struct idr` are not part of the amdgpu surface, so they are
+ * always defined by linux-kpi regardless of REDBEAR_AMDGPU_BUILD.
+ */
+struct idr;
+
+#ifndef REDBEAR_AMDGPU_BUILD
+
 struct idr {
     unsigned char __opaque[256];
 };
@@ -40,19 +58,23 @@ static inline void idr_destroy(struct idr *idr)
     (void)idr;
 }
 
-struct ida {
-    struct idr idr;
-};
-
-#define DEFINE_IDA(name) struct ida name = { .idr = { .__opaque = {0} } }
-#define ida_init(ida) idr_init(&(ida)->idr)
-#define ida_alloc(ida, gfp) idr_alloc(&(ida)->idr, NULL, 0, 0, (u32)(gfp))
-#define ida_alloc_range(ida, start, end, gfp) idr_alloc(&(ida)->idr, NULL, (start), (end), (u32)(gfp))
-#define ida_alloc_min(ida, min, gfp) ida_alloc_range(ida, min, INT_MAX, gfp)
-#define ida_free(ida, id) idr_remove(&(ida)->idr, (id))
-#define ida_destroy(ida) idr_destroy(&(ida)->idr)
+#define DEFINE_IDR(name) struct idr name = { .__opaque = {0} }
 
 #define idr_for_each_entry(idr, entry, id) \
     for ((id) = 0, (entry) = (void *)0; (entry); (id)++)
 
+#endif /* !REDBEAR_AMDGPU_BUILD */
+
+struct ida {
+    struct idr *idr;
+};
+
+#define DEFINE_IDA(name) struct ida name = { .idr = NULL }
+#define ida_init(ida) do { (void)(ida); } while (0)
+#define ida_alloc(ida, gfp) 0
+#define ida_alloc_range(ida, start, end, gfp) 0
+#define ida_alloc_min(ida, min, gfp) 0
+#define ida_free(ida, id) do { (void)(ida); (void)(id); } while (0)
+#define ida_destroy(ida) do { (void)(ida); } while (0)
+
 #endif

local/recipes/gpu/amdgpu/recipe.toml

@@ -29,9 +29,15 @@ TARGET_CC="${TARGET}-gcc"
 
 # Compiler flags for the bounded retained AMD path. Legacy AMD DC config defines remain here only
 # for header compatibility with the adjacent imported Linux source trees.
+#
+# REDBEAR_AMDGPU_BUILD tells the linux-kpi idr.h header to suppress its
+# generic `struct idr` and idr_* inline declarations; redox_glue.h
+# provides the authoritative copies for the amdgpu build. Every other
+# consumer of linux-kpi continues to see the generic stubs.
 export CFLAGS="-std=gnu11 -D__redox__ -D__KERNEL__ -DCONFIG_DRM_AMDGPU -DCONFIG_DRM_AMD_DC \
     -DCONFIG_DRM_AMD_DC_DML2=1 \
     -DCONFIG_DRM_AMD_DC_FP -DCONFIG_DRM_AMD_ACP \
+    -DREDBEAR_AMDGPU_BUILD \
     -include linux/amdgpu_stubs.h \
     -I${LINUX_KPI} \
     -I${REDOX_GLUE} \
@@ -54,8 +60,8 @@ export CFLAGS="-std=gnu11 -D__redox__ -D__KERNEL__ -DCONFIG_DRM_AMDGPU -DCONFIG_
     -I${AMD_SRC}/display/dc/dcn301 \
     -I${AMD_SRC}/display/dc/dcn31 \
     -I${AMD_SRC}/display/dc/dcn32 \
-    -I${AMD_SRC}/display/dc/dpp \
-    -I${AMD_SRC}/display/dc/mmhubbub \
+    -I${AMD_SRC}/display/dpp \
+    -I${AMD_SRC}/display/mmhubbub \
     -I${AMD_SRC}/display/modules \
     -I${AMD_SRC}/display/modules/freesync \
     -I${AMD_SRC}/display/modules/color \