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|
\ Example FCode driver for a hypothetical SCSI bus interface device
hex
\ The following structure defines the registers for the SCSI device.
\ This hypothetical device is designed for ease of programming. It
\ has a separate register for each function (no bit packing). All
\ registers are both readable and writeable. The device has a random-
\ access buffer large enough for a maximum-length SCSI command block.
\ To execute a SCSI command with this device, write the appropriate
\ information into the registers named ">cmd-adr" through ">input?", write
\ a 1 to the ">start" register, and wait for the ">start" register to
\ change to 0. Then read the ">phase" register to determine whether or
\ not the command completed all phases (">phase" reports 0 on success,
\ h# fd for incoming reset, h# ff for other hardware error).
\ If so, ">status" contains the SCSI status byte, and ">message-in"
\ contains the command-complete message byte.
struct ( scsi-registers )
0c field >cmd-adr \ Up to 12 command bytes
4 field >cmd-len \ Length of command block
4 field >data-adr \ Base address of DMA data area
4 field >data-len \ Length of data area
1 field >host-selectid \ Host's selection ID
1 field >target-selectid \ Target's selection ID
1 field >input? \ 1 for data output; 0 for data input
1 field >message-out \ Outgoing message byte
1 field >start \ Write 1 to start. Reads as 0 when done.
1 field >phase \ Reports the last transaction phase
1 field >status \ Returned status byte
1 field >message-in \ Incoming message byte
1 field >intena \ Write 1 to enable interrupts.
1 field >reset-bus \ Write 1 to reset the SCSI bus.
1 field >reset-board \ Write 1 to reset the board.
constant /scsi-regs
\ Now that we have a symbolic name for the size of the register block,
\ we can declare the "reg" property.
\ Registers begin at offset 800000 and continue for "/scsi-regs" bytes.
my-address 80.0000 + my-space /scsi-regs reg
-1 instance value regs \ Virtual base address of device registers
0 instance value my-id \ host adapter's selection ID
0 instance value his-id \ target's selection ID
0 instance value his-lun \ target's unit number
\ Map device registers
: map ( -- )
my-address 80.0000 + my-space /scsi-regs ( addr-low addr-high size )
" map-in" $call-parent to regs ( )
;
: unmap ( -- )
regs /scsi-regs " map-out" $call-parent -1 to regs
;
create reset-done-time 0 ,
create resetting false ,
\ 5 seconds appears to be about the right length of time to wait after
\ a reset, considering a variety of disparate devices.
d# 5000 value scsi-reset-delay
: reset-wait ( -- )
resetting @ if
begin get-msecs reset-done-time @ - 0>= until
resetting off
then
;
: reset-scsi-bus ( -- )
1 regs >reset-board rb! \ Reset the controller board.
0 regs >intena rb! \ Turn off interrupts.
1 regs >reset-bus rb! \ Reset the SCSI bus.
\ After resetting the SCSI bus, we have to give the target devices
\ some time to initialize their microcode. Otherwise the first command
\ may hang, as with some older controllers. We note the time when it
\ is okay to access the bus (now plus some delay), and "execute-command"
\ will delay until that time is reached, if necessary.
\ This allows us to overlap the delay with other work in many cases.
get-msecs scsi-reset-delay + reset-done-time ! resetting on
;
0 value scsi-time \ Maximum command time in milliseconds
0 value time-limit \ Ending time for command
: set-timeout ( msecs -- ) to scsi-time ;
0 value devaddr
\ Returns true if select failed
: (exec) ( dma-adr,len dir cmd-adr,len -- hwresult )
reset-wait \ Delay until any prior reset operation is done.
his-lun h# 80 or regs >message-out rb! \ Set unit number; no disconnect.
my-id regs >host-selectid rb! \ Set the selection IDs.
his-id regs >target-selectid rb!
\ Write the command block into the host adapter's command register
dup 0 ?do ( data-adr,len dir cmd-adr,len )
over i + c@ ( data-adr,len dir cmd-adr,len cmd-byte )
regs >cmd-adr i ca+ rb! ( data-adr,len dir cmd-adr,len )
loop ( data-adr,len dir cmd-adr,len )
regs >cmd-len rl! drop ( data-adr,len dir )
\ Set the data transfer parameters.
( .. dir ) regs >input? rb! ( data-adr,len ) \ Direction
( .. len ) regs >data-len rl! ( data-adr ) \ Length
( .. adr ) regs >data-adr rl! ( ) \ DMA Address
\ Now we're ready to execute the command.
1 regs >start rb! \ Tell board to start the command.
get-msecs scsi-time + to time-limit \ Set the time limit.
begin regs >start rb@ while \ Wait until command finished.
scsi-time if \ If timeout is enabled, and
get-msecs time-limit - 0>= if \ the time-limit has been reached,
reset-scsi-bus true exit \ reset the bus and return error.
then
then
repeat
\ Nonzero phase means that the command didn't finish.
regs >phase rb@
;
\ Returns true if select failed
: execute-command ( data-adr,len dir cmd-adr,len -- hwresult | statbyte false)
\ Temporarily put dir and cmd-adr,len on the return stack to get them
\ out of the way so we can work on the DMA data buffer.
>r >r >r ( data-adr,len )
dup if ( data-adr,len )
\ If the data transfer has a nonzero length, we have to map it in.
2dup false dma-map-in ( data-adr,len dma )
2dup swap r> r> r> ( data-adr,len dma dma,len dir cmd-adr,len)
(exec) ( data-adr,len phys hwres)
>r swap dma-map-out r> ( hwresult )
else ( data-adr,len )
r> r> r> (exec) ( hwresult )
then ( hwresult )
?dup 0= if ( hwresult | )
regs >status rb@ false \ Command finished; return status byte and false.
then ( hwresult | statbyte 0 )
;
external
: reset ( -- ) map reset-scsi-bus unmap ;
reset \ Reset the SCSI bus when we are probed.
: open-hardware ( -- okay? )
map
7 to my-id
\ Should perform a quick "sanity check" selftest here,
\ returning true if the test succeeds.
true
;
: reopen-hardware ( -- okay? ) true ;
: close-hardware ( -- ) unmap ;
: reclose-hardware ( -- ) ;
: selftest ( -- 0 | error-code )
\ Perform reasonably extensive selftest here, displaying
\ a message and returning an error code if the
\ test fails and returning 0 if the test succeeds.
0
;
: set-address ( unit target -- )
to his-id to his-lun
;
|
