Index: sys/dev/fdt/fdt_slicer.c
===================================================================
--- sys/dev/fdt/fdt_slicer.c
+++ sys/dev/fdt/fdt_slicer.c
@@ -43,7 +43,7 @@
 #endif
 
 int
-flash_fill_slices(device_t dev, struct flash_slice *slices, int *slices_num)
+fdt_flash_fill_slices(device_t dev, struct flash_slice *slices, int *slices_num)
 {
 	char *slice_name;
 	phandle_t dt_node, dt_child;
Index: sys/dev/nand/nfc_rb.c
===================================================================
--- sys/dev/nand/nfc_rb.c
+++ sys/dev/nand/nfc_rb.c
@@ -40,6 +40,7 @@
 #include <sys/rman.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/slicer.h>
 #include <sys/time.h>
 
 #include <machine/bus.h>
@@ -47,6 +48,7 @@
 #include <dev/ofw/ofw_bus.h>
 #include <dev/ofw/ofw_bus_subr.h>
 
+#include <geom/geom_disk.h>
 #include <dev/nand/nand.h>
 #include <dev/nand/nandbus.h>
 
@@ -111,6 +113,39 @@
 };
 #endif
 
+/* Slicer operates on the controller, so we have to find the chip. */
+static int
+rb_nand_slicer(device_t dev, struct flash_slice *slices, int *nslices)
+{
+	struct nand_chip *chip;
+	device_t *children;
+	int n;
+
+	if (device_get_children(dev, &children, &n) != 0) {
+		panic("Slicer called on controller with no child!");
+	}
+	dev = children[0];
+	free(children, M_TEMP);
+
+	if (device_get_children(dev, &children, &n) != 0) {
+		panic("Slicer called on controller with nandbus but no child!");
+	}
+	dev = children[0];
+	free(children, M_TEMP);
+
+	chip = device_get_softc(dev);
+	*nslices = 2;
+	slices[0].base = 0;
+	slices[0].size = 4 * 1024 * 1024;
+	slices[0].label = "boot";
+
+	slices[1].base = 4 * 1024 * 1024;
+	slices[1].size = chip->ndisk->d_mediasize - slices[0].size;
+	slices[1].label = "rootfs";
+
+	return (0);
+}
+
 static int
 rb_nand_probe(device_t dev)
 {
@@ -180,6 +215,7 @@
 		return (ENXIO);
 	}
 
+	flash_register_slicer(rb_nand_slicer);
 	nand_init(&sc->nand_dev, dev, NAND_ECC_SOFT, 0, 0, NULL, NULL);
 
 	err = nandbus_create(dev);
Index: sys/geom/geom_flashmap.c
===================================================================
--- sys/geom/geom_flashmap.c
+++ sys/geom/geom_flashmap.c
@@ -70,6 +70,8 @@
 static void g_flashmap_config(struct gctl_req *, struct g_class *,
     const char *);
 static int g_flashmap_load(device_t, struct g_flashmap_head *);
+static int (*flash_fill_slices)(device_t, struct flash_slice *, int *) =
+    fdt_flash_fill_slices;
 
 MALLOC_DECLARE(M_FLASHMAP);
 MALLOC_DEFINE(M_FLASHMAP, "geom_flashmap", "GEOM flash memory slicer class");
@@ -230,7 +232,8 @@
 
 	buf_size = sizeof(struct flash_slice) * FLASH_SLICES_MAX_NUM;
 	slices = malloc(buf_size, M_FLASHMAP, M_WAITOK | M_ZERO);
-	if (flash_fill_slices(dev, slices, &nslices) == 0) {
+	if (flash_fill_slices &&
+	    flash_fill_slices(dev, slices, &nslices) == 0) {
 		for (i = 0; i < nslices; i++) {
 			slice = malloc(sizeof(struct g_flashmap_slice),
 			    M_FLASHMAP, M_WAITOK);
@@ -247,6 +250,12 @@
 	return (nslices);
 }
 
+void flash_register_slicer(int (*slicer)(device_t, struct flash_slice *, int *))
+{
+
+	flash_fill_slices = slicer;
+}
+
 static struct g_class g_flashmap_class = {
 	.name = FLASHMAP_CLASS_NAME,
 	.version = G_VERSION,
Index: sys/sys/slicer.h
===================================================================
--- sys/sys/slicer.h
+++ sys/sys/slicer.h
@@ -45,7 +45,8 @@
 };
 
 #ifdef _KERNEL
-int flash_fill_slices(device_t, struct flash_slice *, int *);
+int fdt_flash_fill_slices(device_t, struct flash_slice *, int *) __weak_symbol;
+void flash_register_slicer(int (*)(device_t, struct flash_slice *, int *));
 #endif /* _KERNEL */
 
 #endif /* _FLASH_SLICER_H_ */