egl: add EGL_EXT_device_drm support

Add implementation based around the drmDevice API. As such it's only
available only when building with libdrm. With the latter already a
requirement when using !SW code paths in the platform code.

Note: the current code will work if a device is hot-plugged. Yet
hot-unplugged is not implemented, since I have no ways of testing it.

v2:
 - ddd some _eglDeviceSupports checks
 - require DRM_NODE_RENDER
 - add _eglGetDRMDeviceRenderNode helper

v3:
 - flip inverted asserts (Mathias)

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Mathias Fröhlich <Mathias.Froehlich@web.de>

src/egl/main/egldevice.c

@@ -25,10 +25,14 @@
  *
  **************************************************************************/
 
+#ifdef HAVE_LIBDRM
+#include <xf86drm.h>
+#endif
 #include "util/macros.h"
 
 #include "eglcurrent.h"
 #include "egldevice.h"
+#include "egllog.h"
 #include "eglglobals.h"
 #include "egltypedefs.h"
 
@@ -39,6 +43,11 @@ struct _egl_device {
    const char *extensions;
 
    EGLBoolean MESA_device_software;
+   EGLBoolean EXT_device_drm;
+
+#ifdef HAVE_LIBDRM
+   drmDevicePtr device;
+#endif
 };
 
 void
@@ -60,6 +69,10 @@ _eglFiniDevice(void)
       dev = dev_list;
       dev_list = dev_list->Next;
 
+#ifdef HAVE_LIBDRM
+      assert(_eglDeviceSupports(dev, _EGL_DEVICE_DRM));
+      drmFreeDevice(&dev->device);
+#endif
       free(dev);
    }
 
@@ -87,6 +100,55 @@ _EGLDevice _eglSoftwareDevice = {
    .MESA_device_software = EGL_TRUE,
 };
 
+#ifdef HAVE_LIBDRM
+/*
+ * Negative value on error, zero if newly added, one if already in list.
+ */
+static int
+_eglAddDRMDevice(drmDevicePtr device, _EGLDevice **out_dev)
+{
+   _EGLDevice *dev;
+
+   if ((device->available_nodes & (1 << DRM_NODE_PRIMARY |
+                                   1 << DRM_NODE_RENDER)) == 0)
+      return -1;
+
+   dev = _eglGlobal.DeviceList;
+
+   /* The first device is always software */
+   assert(dev);
+   assert(_eglDeviceSupports(dev, _EGL_DEVICE_SOFTWARE));
+
+   while (dev->Next) {
+      dev = dev->Next;
+
+      assert(_eglDeviceSupports(dev, _EGL_DEVICE_DRM));
+      if (drmDevicesEqual(device, dev->device) != 0) {
+         if (out_dev)
+            *out_dev = dev;
+         return 1;
+      }
+   }
+
+   dev->Next = calloc(1, sizeof(_EGLDevice));
+   if (!dev->Next) {
+      if (out_dev)
+         *out_dev = NULL;
+      return -1;
+   }
+
+   dev = dev->Next;
+   dev->extensions = "EGL_EXT_device_drm";
+   dev->EXT_device_drm = EGL_TRUE;
+   dev->device = device;
+
+   if (out_dev)
+      *out_dev = dev;
+
+   return 0;
+}
+#endif
+
 /* Adds a device in DeviceList, if needed for the given fd.
  *
  * If a software device, the fd is ignored.
@@ -105,7 +167,21 @@ _eglAddDevice(int fd, bool software)
    if (software)
       goto out;
 
+#ifdef HAVE_LIBDRM
+   drmDevicePtr device;
+
+   if (drmGetDevice2(fd, 0, &device) != 0) {
+      dev = NULL;
+      goto out;
+   }
+
+   /* Device is not added - error or already present */
+   if (_eglAddDRMDevice(device, &dev) != 0)
+      drmFreeDevice(&device);
+#else
+   _eglLog(_EGL_FATAL, "Driver bug: Built without libdrm, yet looking for HW device");
    dev = NULL;
+#endif
 
 out:
    mtx_unlock(_eglGlobal.Mutex);
@@ -118,12 +194,26 @@ _eglDeviceSupports(_EGLDevice *dev, _EGLDeviceExtension ext)
    switch (ext) {
    case _EGL_DEVICE_SOFTWARE:
       return dev->MESA_device_software;
+   case _EGL_DEVICE_DRM:
+      return dev->EXT_device_drm;
    default:
       assert(0);
       return EGL_FALSE;
    };
 }
 
+/* Ideally we'll have an extension which passes the render node,
+ * instead of the card one + magic.
+ *
+ * Then we can move this in _eglQueryDeviceStringEXT below. Until then
+ * keep it separate.
+ */
+const char *
+_eglGetDRMDeviceRenderNode(_EGLDevice *dev)
+{
+   return dev->device->nodes[DRM_NODE_RENDER];
+}
+
 EGLBoolean
 _eglQueryDeviceAttribEXT(_EGLDevice *dev, EGLint attribute,
                          EGLAttrib *value)
@@ -141,6 +231,12 @@ _eglQueryDeviceStringEXT(_EGLDevice *dev, EGLint name)
    switch (name) {
    case EGL_EXTENSIONS:
       return dev->extensions;
+#ifdef HAVE_LIBDRM
+   case EGL_DRM_DEVICE_FILE_EXT:
+      if (_eglDeviceSupports(dev, _EGL_DEVICE_DRM))
+         return dev->device->nodes[DRM_NODE_PRIMARY];
+      /* fall through */
+#endif
    default:
       _eglError(EGL_BAD_PARAMETER, "eglQueryDeviceStringEXT");
       return NULL;
@@ -167,6 +263,23 @@ _eglRefreshDeviceList(void)
    assert(_eglDeviceSupports(dev, _EGL_DEVICE_SOFTWARE));
    count++;
 
+#ifdef HAVE_LIBDRM
+   drmDevicePtr devices[64];
+   int num_devs, ret;
+
+   num_devs = drmGetDevices2(0, devices, ARRAY_SIZE(devices));
+   for (int i = 0; i < num_devs; i++) {
+      ret = _eglAddDRMDevice(devices[i], NULL);
+
+      /* Device is not added - error or already present */
+      if (ret != 0)
+         drmFreeDevice(&devices[i]);
+
+      if (ret >= 0)
+         count++;
+   }
+#endif
+
    return count;
 }
 

src/egl/main/egldevice.h

@@ -60,6 +60,7 @@ _eglAddDevice(int fd, bool software);
 
 enum _egl_device_extension {
    _EGL_DEVICE_SOFTWARE,
+   _EGL_DEVICE_DRM,
 };
 
 typedef enum _egl_device_extension _EGLDeviceExtension;
@@ -67,6 +68,9 @@ typedef enum _egl_device_extension _EGLDeviceExtension;
 EGLBoolean
 _eglDeviceSupports(_EGLDevice *dev, _EGLDeviceExtension ext);
 
+const char *
+_eglGetDRMDeviceRenderNode(_EGLDevice *dev);
+
 EGLBoolean
 _eglQueryDeviceAttribEXT(_EGLDevice *dev, EGLint attribute,
                          EGLAttrib *value);