intel: Add experimental rendernode support

Render nodes allow clients full access to off-screen rendering and GPU
offload, without assuming any master responsiblities (for device and
display management). As they have a more limited interface, they can be
used in a more permissive manner.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

4 files changed, 60 insertions, 9 deletions

diff --git a/configure.ac b/configure.ac
index 9fc011ec..1e73c0c1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -336,6 +336,17 @@ fi
 
 xp_msg=""
 
+AC_ARG_ENABLE(rendernode,
+	      AS_HELP_STRING([--enable-rendernode],
+			     [Enable use of render nodes (experimental) [default=no]]),
+	      [RENDERNODE="$enableval"],
+	      [RENDERNODE=no])
+AM_CONDITIONAL(USE_RENDERNODE, test x$RENDERNODE = xyes)
+if test "x$RENDERNODE" = xyes; then
+	AC_DEFINE(USE_RENDERNODE,1,[Assume "rendernode" support])
+	xp_msg="$xp_msg rendernode"
+fi
+
 AC_ARG_ENABLE(create2,
 	      AS_HELP_STRING([--enable-create2],
 			     [Enable use of create2 ioctl (experimental) [default=no]]),
diff --git a/src/intel_device.c b/src/intel_device.c
index d9ff8bcc..751875e3 100644
--- a/src/intel_device.c
+++ b/src/intel_device.c
@@ -24,6 +24,12 @@
 
  **************************************************************************/
 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <sys/types.h>
+#include <sys/stat.h>
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>
@@ -43,7 +49,8 @@
 #include "intel_driver.h"
 
 struct intel_device {
-	char *path;
+	char *master_node;
+	char *render_node;
 	int fd;
 	int open_count;
 	int master_count;
@@ -164,6 +171,32 @@ static int __intel_open_device(const struct pci_device *pci, char **path)
 	return fd;
 }
 
+static char *find_render_node(int fd)
+{
+#if defined(USE_RENDERNODE)
+	struct stat master, render;
+	char buf[128];
+
+	if (fstat(fd, &master))
+		return NULL;
+
+	if (!S_ISCHR(master.st_mode))
+		return NULL;
+
+	/* Are we a render-node ourselves? */
+	if (master.st_rdev & 0x80)
+		return NULL;
+
+	sprintf(buf, "/dev/dri/renderD%d", (int)((master.st_rdev | 0x80) & 0xff));
+	if (stat(buf, &render) == 0 &&
+	    master.st_mode == render.st_mode &&
+	    render.st_rdev == (master.st_rdev | 0x80))
+		return strdup(buf);
+#endif
+
+	return NULL;
+}
+
 int intel_open_device(int entity_num,
 		      const struct pci_device *pci,
 		      const char *path)
@@ -194,10 +227,13 @@ int intel_open_device(int entity_num,
 	if (dev == NULL)
 		goto err_close;
 
-	dev->path = local_path;
 	dev->fd = fd;
 	dev->open_count = 0;
 	dev->master_count = 0;
+	dev->master_node = local_path;
+	dev->render_node = find_render_node(fd);
+	if (dev->render_node == NULL)
+		dev->render_node = dev->master_node;
 
 	/* If hosted under a system compositor, just pretend to be master */
 	if (hosted()) {
@@ -257,11 +293,11 @@ int intel_get_device(ScrnInfoPtr scrn)
 	return dev->fd;
 }
 
-const char *intel_get_device_name(ScrnInfoPtr scrn)
+const char *intel_get_client_name(ScrnInfoPtr scrn)
 {
 	struct intel_device *dev = intel_device(scrn);
-	assert(dev && dev->path);
-	return dev->path;
+	assert(dev && dev->render_node);
+	return dev->render_node;
 }
 
 int intel_get_master(ScrnInfoPtr scrn)
@@ -312,7 +348,9 @@ void __intel_uxa_release_device(ScrnInfoPtr scrn)
 		intel_set_device(scrn, NULL);
 
 		drmClose(dev->fd);
-		free(dev->path);
+		if (dev->render_node != dev->master_node)
+			free(dev->render_node);
+		free(dev->master_node);
 		free(dev);
 	}
 }
@@ -331,6 +369,8 @@ void intel_put_device(ScrnInfoPtr scrn)
 	intel_set_device(scrn, NULL);
 
 	drmClose(dev->fd);
-	free(dev->path);
+	if (dev->render_node != dev->master_node)
+		free(dev->render_node);
+	free(dev->master_node);
 	free(dev);
 }
diff --git a/src/intel_driver.h b/src/intel_driver.h
index 47685364..e54054fe 100644
--- a/src/intel_driver.h
+++ b/src/intel_driver.h
@@ -122,7 +122,7 @@ void intel_detect_chipset(ScrnInfoPtr scrn,
 
 int intel_open_device(int entity_num, const struct pci_device *pci, const char *path);
 int intel_get_device(ScrnInfoPtr scrn);
-const char *intel_get_device_name(ScrnInfoPtr scrn);
+const char *intel_get_client_name(ScrnInfoPtr scrn);
 int intel_get_master(ScrnInfoPtr scrn);
 int intel_put_master(ScrnInfoPtr scrn);
 void intel_put_device(ScrnInfoPtr scrn);
diff --git a/src/sna/sna_dri.c b/src/sna/sna_dri.c
index ff960759..f31ca4e9 100644
--- a/src/sna/sna_dri.c
+++ b/src/sna/sna_dri.c
@@ -2321,7 +2321,7 @@ bool sna_dri_open(struct sna *sna, ScreenPtr screen)
 	memset(&info, '\0', sizeof(info));
 	info.fd = sna->kgem.fd;
 	info.driverName = dri_driver_name(sna);
-	info.deviceName = intel_get_device_name(sna->scrn);
+	info.deviceName = intel_get_client_name(sna->scrn);
 
 	DBG(("%s: loading dri driver '%s' [gen=%d] for device '%s'\n",
 	     __FUNCTION__, info.driverName, sna->kgem.gen, info.deviceName));