7 ! setup.S Copyright (C) 1991, 1992 Linus Torvalds
9 ! setup.s is responsible for getting the system data from the BIOS,
10 ! and putting them into the appropriate places in system memory.
11 ! both setup.s and system has been loaded by the bootblock.
13 /* we're getting screwed again and again by this problem of the 8259.
14 * so we're going to leave this lying around for inclusion into
15 * crt0.S on an as-needed basis.
16 ! well, that went ok, I hope. Now we have to reprogram the interrupts :-(
17 ! we put them right after the intel-reserved hardware interrupts, at
18 ! int 0x20-0x2F. There they won't mess up anything. Sadly IBM really
19 ! messed this up with the original PC, and they haven't been able to
20 ! rectify it afterwards. Thus the bios puts interrupts at 0x08-0x0f,
21 ! which is used for the internal hardware interrupts as well. We just
22 ! have to reprogram the 8259's, and it isn't fun.
25 void setup_i8259(void)
27 outb(0x11, 0x20); /*! initialization sequence to 8259A-1*/
28 outb(0x11, 0xA0); /*! and to 8259A-2*/
29 outb(0x20, 0x21); /*! start of hardware int's (0x20)*/
30 outb(0x28, 0xA1); /*! start of hardware int's 2 (0x28)*/
31 outb(0x04, 0x21); /*! 8259-1 is master*/
32 outb(0x02, 0xA1); /*! 8259-2 is slave*/
33 outb(0x01, 0x21); /*! 8086 mode for both*/
35 outb(0xFF, 0xA1); /*! mask off all interrupts for now*/
36 outb(0xFB, 0x21); /*! mask all irq's but irq2 which is cascaded*/
40 * I like the way Linus says it:
41 ! Well, that certainly wasn't fun :-(. Hopefully it works, and we don't
42 ! need no steenking BIOS anyway (except for the initial loading :-).