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CosmOS Block Devices and Filesystems

Cosmos defines devices for:

  • Disk Controllers (ata0, ata1...)
  • Disks (disk0, disk1,...)
  • Parition tables (pt0, pt1.. etc)
  • Partitions (part0, part1,...
  • FileSystems (fat0, sfs0,...etc)

Each layer builds upon the next layer. When Cosmos detects an IDE disk controller, such as ata0, it then defines disks for each of

  • Primary Master
  • Primary Slave
  • Secondary Master
  • Secondary Slave

These will show up as disk0, disk1, disk2, disk3.

CosmOS doesn't automatically read the partition table and mount disks (yet). To mount a disk, we use the partition table device.

The below code creates a partition table device for an MBR partition table on disk0. Running this code will result in

  • creating a pt device such as pt0, for the MBR partition table
  • creating multiple part devices such as part0, part1, part2 for each partition.
	struct device* dsk = devicemgr_find_device("disk0");
	if (0 != dsk) {
		struct device* dev = mbr_pt_attach(dsk);
		struct deviceapi_part_table* api = (struct deviceapi_part_table*)dev->api;
		mbr_pt_detach(dev);
	} else {
		kprintf("Unable to find disk0\n", devicename);
	}

Now that CosmOS knows about the partitions, we can mount filesystems on them. This code creates a FAT device such as `fat0' on 'part0'.

	struct device* part = devicemgr_find_device("part0");
	if (0 != part) {
		struct device* dev = fat_attach(part);
		fat_detach(part);
	} else {
		kprintf("Unable to find part0\n", devicename);
	}

The device API's that each device type expose are: