fb: add rudimentary drm fb and page api

This implementation uses a page flipping thread and very simple
pthreads mutex/condition variable synchronization.  There is room
for improvement, but this combined with 3 fb pages enables the
rendering loop to fully overlap with page flipping with the next
ready page queued asynchronously.

1 files changed, 37 insertions, 0 deletions

diff --git a/fb.h b/fb.h
new file mode 100644
index 0000000..13f6bcd
--- /dev/null
+++ b/fb.h
@@ -0,0 +1,37 @@
+#ifndef _FB_H
+#define _FB_H
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <xf86drmMode.h> /* for drmModeModeInfoPtr */
+
+/* All renderers should target fb_fragment_t, which may or may not represent
+ * a full-screen mmap.  Helpers are provided for subdividing fragments for
+ * concurrent renderers.
+ */
+typedef struct fb_fragment_t {
+	uint32_t	*buf;		/* pointer to the first pixel in the fragment */
+	unsigned	x, y;		/* absolute coordinates of the upper left corner of this fragment */
+	unsigned	width, height;	/* width and height of this fragment */
+	unsigned	stride;		/* number of bytes from the end of one row to the start of the next */
+} fb_fragment_t;
+
+/* This is a page handle object for page flip submission/life-cycle.
+ * Outside of fb_page_get()/fb_page_put(), you're going to be interested in
+ * fb_fragment_t.  The fragment included here describes the whole page,
+ * it may be divided via fb_fragment_divide().
+ */
+typedef struct fb_page_t {
+	fb_fragment_t	fragment;
+} fb_page_t;
+
+typedef struct fb_t fb_t;
+
+fb_page_t * fb_page_get(fb_t *fb);
+void fb_page_put(fb_t *fb, fb_page_t *page);
+void fb_free(fb_t *fb);
+void fb_get_put_pages_count(fb_t *fb, unsigned *count);
+fb_t * fb_new(int drm_fd, uint32_t crtc_id, uint32_t *connectors, int n_connectors, drmModeModeInfoPtr mode, int n_pages);
+void fb_fragment_divide(fb_fragment_t *fragment, unsigned n_fragments, fb_fragment_t fragments[]);
+
+#endif