util: Add a simple no-op libdrm shim

Make it easier to deal with build configs that do not have libdrm.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21636>

src/util/libdrm.h

@@ -0,0 +1,80 @@
+/*
+ * Copyright © 2023 Google, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+/*
+ * A simple header that either gives you the real libdrm or a no-op shim,
+ * depending on whether HAVE_LIBDRM is defined.  This is intended to avoid
+ * the proliferation of #ifdef'ery to support environments without libdrm.
+ */
+
+#ifdef HAVE_LIBDRM
+#include <xf86drm.h>
+#else
+
+#include <errno.h>
+
+#define DRM_NODE_PRIMARY 0
+#define DRM_NODE_CONTROL 1
+#define DRM_NODE_RENDER  2
+#define DRM_NODE_MAX     3
+
+#define DRM_BUS_PCI       0
+#define DRM_BUS_USB       1
+#define DRM_BUS_PLATFORM  2
+#define DRM_BUS_HOST1X    3
+
+typedef struct _drmDevice {
+    char **nodes; /* DRM_NODE_MAX sized array */
+    int available_nodes; /* DRM_NODE_* bitmask */
+    int bustype;
+    /* ... */
+} drmDevice, *drmDevicePtr;
+
+static inline int
+drmGetDevices2(uint32_t flags, drmDevicePtr devices[], int max_devices)
+{
+   return -ENOENT;
+}
+
+static inline void
+drmFreeDevices(drmDevicePtr devices[], int count) {}
+
+typedef struct _drmVersion {
+    int     version_major;        /**< Major version */
+    int     version_minor;        /**< Minor version */
+    int     version_patchlevel;   /**< Patch level */
+    int     name_len;             /**< Length of name buffer */
+    char    *name;                /**< Name of driver */
+    int     date_len;             /**< Length of date buffer */
+    char    *date;                /**< User-space buffer to hold date */
+    int     desc_len;             /**< Length of desc buffer */
+    char    *desc;                /**< User-space buffer to hold desc */
+} drmVersion, *drmVersionPtr;
+
+static inline struct _drmVersion *
+drmGetVersion(int fd) { return NULL; }
+
+static inline void
+drmFreeVersion(struct _drmVersion *v) {}
+
+#endif