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MiNT 0.96 pl14

Here are some notes on writing device drivers; before reading

them, you should familiarize yourself with the information in

"filesys.doc", especially the material on device drivers.



Serial Port Device Drivers



Serial port device drivers should recognize the

following ioctl calls:

(here "f" is always a FILEPTR referring to an open

file on the device)





ioctl(f, TIOCIBAUD, long *r):



Set input speed. "r" is a pointer to a 32 bit value, and is both an

input and output parameter. If *r is > 0, it represents the value

to which the serial port's input speed should be set. This value

is a long word representation of the speed in bits per second,

e.g. to set 9600 bits per second *r should be 9600L.

If *r is 0, it indicates that DTR should be dropped.

If *r is < 0, the call is an inquiry call only.



On return, *r is set to the value of the input speed before the

ioctl call was made. If, for some reason, this value is unknown,

*r is set to -1L.



Returns:

0 on success

ERANGE if the requested input speed is not available. In this case,

the next lowest legal input speed available is returned in *r.







ioctl(f, TIOCOBAUD, long *r):



Set output speed. "r" is a pointer to a 32 bit value, and is both an

input and output parameter. If *r is > 0, it represents the value

to which the serial port's output speed should be set. This value

is a long word representation of the speed in bits per second,

e.g. to set 9600 bits per second *r should be 9600L.

If *r is 0, it indicates that the device should be hung up, i.e.

that DTR should no longer be asserted.

If *r is < 0, no change is to be made to the output speed.



On return, *r is set to the value of the output speed before the

ioctl call was made. If, for some reason, this value is unknown,

*r is set to -1L.



Returns:

0 on success

ERANGE if the requested output speed is not available. In this case,

the next lowest legal output speed available is returned in *r.



Note: For many devices both the input and output speeds must always be

the same. For such devices, TIOCIBAUD and TIOCOBAUD may affect both

input and output speed.







ioctl(f, TIOCSBRK, dummy):



Causes a BREAK condition to be set on the output line.

Returns:

0 on success

EINVFN if the serial port cannot send BREAK







ioctl(f, TIOCCBRK, dummy)



Causes any existing BREAK condition to be cleared.

Returns:

0 on success

EINVFN if the serial port cannot send BREAK







ioctl(f, TIOCGFLAGS, short *flags)



Get the terminal control flags bits. 16 bit flag word

pointed to by "flags" is set to reflect the current

terminal state, as follows:



TF_STOPBITS	0x0003

The two low order bits describe the stop bits:

0x0000	illegal -- attempts to set this value are

	ignored

0x0001	1 stop bit

0x0002	1.5 stop bits

0x0003	2 stop bits



TF_CHARBITS	0x000C

The next two bits describe the number of bits

transmitted per character:

0x0000	8 bits per character

0x0004	7 bits per character

0x0008	6 bits per character

0x000C	5 bits per character



The final nybble contains miscellaneous flags:

T_TANDEM	0x1000		^S/^Q flow control active

T_RTSCTS	0x2000		RTS/CTS flow control active

T_EVENP		0x4000		even parity enabled

T_ODDP		0x8000		odd parity enabled

	(note: T_EVENPAR and T_ODDPAR are mutually exclusive)



All other bits are reserved, and should be set to 0.



Returns:

0 on success







ioctl(f, TIOCSFLAGS, short *flags)



Set the terminal control flags (see the description

of TIOCGFLAGS for details) based on the values in the

word pointed to by "flags".



Returns:

0 on success

ERANGE if an illegal or unsupported combination of flags

 is detected.





INTERFACE WITH EXISTING TIOCSETP/TIOCGETP CALLS:



The MiNT kernel will automatically make appropriate

TIOCIBAUD, TIOCOBAUD, TIOCGFLAGS, and TIOCSFLAGS calls

whenever a TIOCSETP or TIOCGETP Fcntl is made on a

terminal. The kernel will convert a Unix style baud

specification into a MiNT style one, as follows:



value of sg_ispeed or	     value sent to

     sg_ospeed		         driver

#define B0     0		    0L

#define B50    1		   50L

#define B75    2		   75L

#define B110   3		  110L

#define B134   4		  134L

#define B150   5		  150L

#define B200   6		  200L

#define B300   7		  300L

#define B600   8		  600L

#define B1200  9		 1200L

#define B1800  10		 1800L

#define B2400  11		 2400L

#define B4800  12		 4800L

#define B9600  13		 9600L

#define B19200 14		19200L

#define B38400 15		38400L (*)



anything else			   -1L





(*) 38400 baud is not supported by the built

in device drivers, but may be by external drivers



If a speed other than those listed above is desired, the

TIOCIBAUD and/or TIOCOBAUD Fcntls should be used directly.

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