question regarding blk_rq_pos() calls in block.c

In the driver block.c there is this line:

	do {
		struct mmc_command cmd;
		u32 readcmd, writecmd, status = 0;

		memset(&brq, 0, sizeof(struct mmc_blk_request));
		brq.mrq.cmd = &brq.cmd;
		brq.mrq.data = &brq.data;

		// THIS LINE
		brq.cmd.arg = blk_rq_pos(req);

I saw the sector number is a 64 bit number, so can the sector be considered a 'unique number', kind of like a unique address?

I don't see block.c actually using an address to set up a queue request read/write; rather, just sector, block size, command, and # of sectors.
That is why I was wondering.

Thanks for the help and insight.

J (James/Jay) Freyensee
Storage Technology Group
Intel Corporation