Add support for vblank events

The kernel will now write data to the DRM fd for various event types if
requested.  Currently, the only supported event is a vblank event: it contains
the vblank count for the event as well as a timestamp from when the event
ocurred.  Since the DRM fd is now pollable, it's easy to integrate into
existing event loops.

3 files changed, 90 insertions, 0 deletions

diff --git a/libdrm/xf86drm.h b/libdrm/xf86drm.h
index c1d173c44..2cb9c9e98 100644
--- a/libdrm/xf86drm.h
+++ b/libdrm/xf86drm.h
@@ -271,6 +271,7 @@ typedef struct _drmTextureRegion {
 typedef enum {
     DRM_VBLANK_ABSOLUTE = 0x0,	/**< Wait for specific vblank sequence number */
     DRM_VBLANK_RELATIVE = 0x1,	/**< Wait for given number of vblanks */
+    DRM_VBLANK_EVENT = 0x4000000,	/**< Send event instead of blocking */
     DRM_VBLANK_FLIP = 0x8000000,	/**< Scheduled buffer swap should flip */
     DRM_VBLANK_NEXTONMISS = 0x10000000,	/**< If missed, wait for next vblank */
     DRM_VBLANK_SECONDARY = 0x20000000,	/**< Secondary display controller */
@@ -667,4 +668,22 @@ extern void drmMsg(const char *format, ...);
 extern int drmSetMaster(int fd);
 extern int drmDropMaster(int fd);
 
+#define DRM_EVENT_CONTEXT_VERSION 1
+
+typedef struct _drmEventContext {
+
+	/* This struct is versioned so we can add more pointers if we
+	 * add more events. */
+	int version;
+
+	void (*vblank_handler)(int fd,
+			       unsigned int sequence, 
+			       unsigned int tv_sec,
+			       unsigned int tv_usec,
+			       void *user_data);
+
+} drmEventContext, *drmEventContextPtr;
+
+extern int drmHandleEvent(int fd, drmEventContextPtr evctx);
+
 #endif
diff --git a/libdrm/xf86drmMode.c b/libdrm/xf86drmMode.c
index 88b4fe3af..6d85113a1 100644
--- a/libdrm/xf86drmMode.c
+++ b/libdrm/xf86drmMode.c
@@ -46,6 +46,7 @@
 #include <drm.h>
 #include <string.h>
 #include <dirent.h>
+#include <unistd.h>
 #include <errno.h>
 
 #define U642VOID(x) ((void *)(unsigned long)(x))
@@ -667,3 +668,45 @@ int drmModeCrtcSetGamma(int fd, uint32_t crtc_id, uint32_t size,
 
 	return 0;
 }
+
+int drmHandleEvent(int fd, drmEventContextPtr evctx)
+{
+	char buffer[1024];
+	int len, i;
+	struct drm_event *e;
+	struct drm_event_vblank *vblank;
+	
+	/* The DRM read semantics guarantees that we always get only
+	 * complete events. */
+
+	len = read(fd, buffer, sizeof buffer);
+	if (len == 0)
+		return 0;
+	if (len < sizeof *e)
+		return -1;
+
+	i = 0;
+	while (i < len) {
+		e = (struct drm_event *) &buffer[i];
+		switch (e->type) {
+		case DRM_EVENT_VBLANK:
+			if (evctx->version < 1 ||
+			    evctx->vblank_handler == NULL)
+				break;
+			vblank = (struct drm_event_vblank *) e;
+			evctx->vblank_handler(fd,
+					      vblank->sequence, 
+					      vblank->tv_sec,
+					      vblank->tv_usec,
+					      U642VOID (vblank->user_data));
+			break;
+			
+		default:
+			break;
+		}
+		i += e->length;
+	}
+
+	return 0;
+}
+
diff --git a/shared-core/drm.h b/shared-core/drm.h
index d97844f83..089e184a6 100644
--- a/shared-core/drm.h
+++ b/shared-core/drm.h
@@ -809,6 +809,34 @@ struct drm_gem_open {
 #define DRM_COMMAND_BASE                0x40
 #define DRM_COMMAND_END                 0xA0
 
+/**
+ * Header for events written back to userspace on the drm fd.  The
+ * type defines the type of event, the length specifies the total
+ * length of the event (including the header), and user_data is
+ * typically a 64 bit value passed with the ioctl that triggered the
+ * event.  A read on the drm fd will always only return complete
+ * events, that is, if for example the read buffer is 100 bytes, and
+ * there are two 64 byte events pending, only one will be returned.
+ *
+ * Event types 0 - 0x7fffffff are generic drm events, 0x80000000 and
+ * up are chipset specific.
+ */
+struct drm_event {
+	uint32_t type;
+	uint32_t length;
+};
+
+#define DRM_EVENT_VBLANK 0x01
+
+struct drm_event_vblank {
+	struct drm_event base;
+	uint64_t user_data;
+	uint32_t tv_sec;
+	uint32_t tv_usec;
+	uint32_t sequence;
+	uint32_t reserved;
+};
+
 /* typedef area */
 #ifndef __KERNEL__
 typedef struct drm_clip_rect drm_clip_rect_t;