add drive to access an area on emmc/sd as disk

nyx/nyx_gui/storage/sfd.c

@@ -0,0 +1,42 @@
+#include "sfd.h"
+#include <storage/emmc.h>
+#include <storage/sdmmc.h>
+
+static sdmmc_storage_t *_storage;
+static u32 _offset;
+static u32 _size;
+
+static void ensure_partition(){
+	if(_storage == &emmc_storage){
+		emmc_set_partition(EMMC_GPP);
+	}
+}
+
+int sfd_read(u32 sector, u32 count, void *buff){
+	if(sector + _offset + count > _offset + _size){
+		return 0;
+	}
+	ensure_partition();
+	return sdmmc_storage_read(_storage, sector + _offset, count, buff);
+}
+
+int sfd_write(u32 sector, u32 count, void *buff){
+	if(sector + _offset + count > _offset + _size){
+		return 0;
+	}
+	ensure_partition();
+	return sdmmc_storage_write(_storage, sector + _offset, count, buff);
+}
+
+bool sfd_init(sdmmc_storage_t *storage, u32 offset, u32 size){
+	_storage = storage;
+	_offset = offset;
+	_size = size;
+	return true;
+}
+
+void sfd_end(){
+	_storage = NULL;
+	_offset = 0;
+	_size = 0;
+}