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/*
* linux/kernel/rs_io.s
*
* (C) 1991 Linus Torvalds
*/
/*
* rs_io.s
*
* This module implements the rs232 io interrupts.
*/
.text
.globl rs1_interrupt,rs2_interrupt
size = 1024 /* must be power of two !
and must match the value
in tty_io.c!!! */
/* these are the offsets into the read/write buffer structures */
rs_addr = 0
head = 4
tail = 8
proc_list = 12
buf = 16
startup = 256 /* chars left in write queue when we restart it */
/*
* These are the actual interrupt routines. They look where
* the interrupt is coming from, and take appropriate action.
*/
.align 2
rs1_interrupt:
pushl $table_list+8
jmp rs_int
.align 2
rs2_interrupt:
pushl $table_list+16
rs_int:
pushl %edx
pushl %ecx
pushl %ebx
pushl %eax
push %es
push %ds /* as this is an interrupt, we cannot */
pushl $0x10 /* know that bs is ok. Load it */
pop %ds
pushl $0x10
pop %es
movl 24(%esp),%edx
movl (%edx),%edx
movl rs_addr(%edx),%edx
addl $2,%edx /* interrupt ident. reg */
rep_int:
xorl %eax,%eax
inb %dx,%al
testb $1,%al
jne end
cmpb $6,%al /* this shouldn't happen, but ... */
ja end
movl 24(%esp),%ecx
pushl %edx
subl $2,%edx
call *jmp_table(,%eax,2) /* NOTE! not *4, bit0 is 0 already */
popl %edx
jmp rep_int
end: movb $0x20,%al
outb %al,$0x20 /* EOI */
pop %ds
pop %es
popl %eax
popl %ebx
popl %ecx
popl %edx
addl $4,%esp # jump over _table_list entry
iret
jmp_table:
.long modem_status,write_char,read_char,line_status
.align 2
modem_status:
addl $6,%edx /* clear intr by reading modem status reg */
inb %dx,%al
ret
.align 2
line_status:
addl $5,%edx /* clear intr by reading line status reg. */
inb %dx,%al
ret
.align 2
read_char:
inb %dx,%al
movl %ecx,%edx
subl $table_list,%edx
shrl $3,%edx
movl (%ecx),%ecx # read-queue
movl head(%ecx),%ebx
movb %al,buf(%ecx,%ebx)
incl %ebx
andl $size-1,%ebx
cmpl tail(%ecx),%ebx
je 1f
movl %ebx,head(%ecx)
1: pushl %edx
call do_tty_interrupt
addl $4,%esp
ret
.align 2
write_char:
movl 4(%ecx),%ecx # write-queue
movl head(%ecx),%ebx
subl tail(%ecx),%ebx
andl $size-1,%ebx # nr chars in queue
je write_buffer_empty
cmpl $startup,%ebx
ja 1f
movl proc_list(%ecx),%ebx # wake up sleeping process
testl %ebx,%ebx # is there any?
je 1f
movl $0,(%ebx)
1: movl tail(%ecx),%ebx
movb buf(%ecx,%ebx),%al
outb %al,%dx
incl %ebx
andl $size-1,%ebx
movl %ebx,tail(%ecx)
cmpl head(%ecx),%ebx
je write_buffer_empty
ret
.align 2
write_buffer_empty:
movl proc_list(%ecx),%ebx # wake up sleeping process
testl %ebx,%ebx # is there any?
je 1f
movl $0,(%ebx)
1: incl %edx
inb %dx,%al
jmp 1f
1: jmp 1f
1: andb $0xd,%al /* disable transmit interrupt */
outb %al,%dx
ret
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