Index: uspace/app/mkexfat/mkexfat.c
===================================================================
--- uspace/app/mkexfat/mkexfat.c	(revision acb866ae8543dfb11146d6a3a636f63d40165373)
+++ uspace/app/mkexfat/mkexfat.c	(revision 39aa8ced119bf7e09823acd7771b7350177a3149)
@@ -42,4 +42,21 @@
 #define NAME    "mkexfat"
 
+/** First sector of the FAT */
+#define FAT_SECTOR_START 128
+
+/** Divide and round up. */
+#define div_round_up(a, b) (((a) + (b) - 1) / (b))
+
+typedef struct exfat_cfg {
+	uint64_t volume_start;
+	uint64_t volume_count;
+	uint32_t fat_sector_count;
+	uint32_t data_start_sector;
+	uint32_t data_cluster;
+	uint32_t rootdir_cluster;
+	unsigned bytes_per_sector;
+	unsigned sec_per_cluster;
+} exfat_cfg_t;
+
 static void usage(void)
 {
@@ -47,6 +64,50 @@
 }
 
+/** Initialize the exFAT params structure.
+ *
+ * @param cfg Pointer to the exFAT params structure to initialize.
+ */
+static void
+cfg_params_initialize(exfat_cfg_t *cfg)
+{
+}
+
+/** Initialize the Volume Boot Record fields.
+ *
+ * @param vbr Pointer to the Volume Boot Record structure.
+ * @param cfg Pointer to the exFAT configuration structure.
+ */
+static void
+vbr_initialize(exfat_bs_t *vbr, exfat_cfg_t *cfg)
+{
+	/* Fill the structure with zeroes */
+	memset(vbr, 0, sizeof(exfat_bs_t));
+
+	/* Init Jump Boot section */
+	vbr->jump[0] = 0xEB;
+	vbr->jump[1] = 0x76;
+	vbr->jump[2] = 0x90;
+
+	/* Set the filesystem name */
+	memcpy(vbr->oem_name, "EXFAT   ", sizeof(vbr->oem_name));
+
+	vbr->volume_start = host2uint64_t_le(cfg->volume_start);
+	vbr->volume_count = host2uint64_t_le(cfg->volume_count);
+	vbr->fat_sector_start = host2uint32_t_le(FAT_SECTOR_START);
+	vbr->fat_sector_count = host2uint32_t_le(cfg->fat_sector_count);
+	vbr->version.major = 1;
+	vbr->version.minor = 0;
+	vbr->volume_flags = host2uint16_t_le(0);
+	vbr->bytes_per_sector = cfg->bytes_per_sectors;
+	vbr->sec_per_cluster = cfg->sec_per_cluster;
+	vbr->fat_count = 1;
+	vbr->drive_no = 0x80;
+	vbr->allocated_percent = 0;
+	vbr->signature = host2uint16_t_le(0xAA55);
+}
+
 int main (int argc, char **argv)
 {
+	exfat_cfg_t cfg;
 	aoff64_t dev_nblocks;
 	char *dev_path;
@@ -60,4 +121,7 @@
 		return 1;
 	}
+
+	/* The fist sector of the partition is zero */
+	cfg.volume_start = 0;
 
 	/* TODO: Add parameters */
@@ -86,5 +150,20 @@
 	}
 
+	rc = block_get_nblocks(service_id, &dev_nblocks);
+	if (rc != EOK) {
+		printf(NAME ": Warning, failed to obtain device block size.\n");
+		/* FIXME: the user should specify the filesystem size */
+		return 1;
+	} else {
+		printf(NAME ": Block device has %" PRIuOFF64 " blocks.\n",
+		    dev_nblocks);
+
+		cfg.volume_count = dev_nblocks;
+	}
+
+	cfg_params_initialize(&cfg);
+
 
 	return 0;
 }
+