1 files changed, 141 insertions, 0 deletions
diff --git a/linux/kernel/rs_io.s b/linux/kernel/rs_io.s
new file mode 100644
index 0000000..62f075f
--- /dev/null
+++ b/linux/kernel/rs_io.s
@@ -0,0 +1,141 @@
+/*
+ *	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)
+	pushl %edx
+	call _do_tty_interrupt
+	addl $4,%esp
+1:	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