08/07/2000

Goals: design a user space (and eventually a kernel-space) SCSI Terminal
       Server driver.

Implementation:
	- use SCSI generic driver to access both LUNs of the STS
	- use ptys to attach the STS ports to

Blocks:
	- I have no idea how to pass user-changes of termios back to the
	  STS


Basic operational outline:

- run INQUIRY(s)
- verify that we have the proper device pair (by matching bus/cntrlr/id)
- query device for # of ports
- initialize STS
- open, clear, and initialize STS ports
- open, clear, and initialize ptys
- mark STS write fd as writable
- post initial STS read cmd
- enter processing loop (bulk of run-time)
- exit processing loop
- close PTYs safely
- shutdown and close STS ports
- shutdown STS


The processing loop outline:

- add PTYs without pending STS writes to read set
- add all PTYS to exclusion set
- add STS fds to readset
- add STS fds to exclusion set
- select on fd set
- if STS read fd is readable:
	- process STS packet(s)
	- repost STS read cmd
- for each PTY:
	- if PTY is readable:
		- read PTY
		- buffer reads for future STS writes
- if STS write fd is readable
	- process STS packet(s)
	- mark STS write fd as writable
- if STS write fd is writable
	- build STS packet(s)
	- post STS write cmd
	- mark STS write fd as not writable
- repeat from the top


Some structures:

typeset struct sts_state_t {
	int bus, ctrlr, id;      /* SCSI identifiers */
	char * manufacturer;     /* SCSI manufacturer string */
	char * model;            /* SCSI model string */
	char * rev;              /* SCSI revision */
	int writefd, readfd;     /* write and read fds (LUN 0 and 1) */
	int total_ports;         /* how many ports in the STS */
	struct port_state_t * ports;  /* array of STS port info structures */
	int writable:1;          /* can I post an STS write cmd? */
	int readable:1;          /* can I post an STS read cmd? */
	struct tty_state_t * ttys;  /* array of PTY info structures */
} sts_state;

typeset struct port_state_t {
	int available;      /* is this port usable at all? */
	int writable;       /* is it OK to post an STS writes for this port? */
	/* serial stuff should go here ..... */
} port_state;

typeset struct tty_state_t {
	int ptm;            /* pseudo terminal master fd */
	char * pts_name;    /* strdup'd copy of the pt slave name */
	/* anything else here? ..... */
} tty_state;