cosmopolitan/libc/nexgen32e/sgetc.S

50 lines
2.4 KiB
ArmAsm

/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify │
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License. │
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of │
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software │
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "ape/macros.h"
#include "libc/nexgen32e/uart.h"
#include "libc/notice.inc"
.real
.code16 # .code32 .code64
/ Receives byte over serial line.
/
/ This is both blocking and asynchronous.
/
/ @param di serial port
/ @return ax character received
/ @mode long,legacy,real
/ @see ttytxr
sgetc: push %bp
mov %sp,%bp
mov %di,%dx
add $UART_LSR,%dx
mov $UART_TTYDA,%ah
1: in %dx,%al
and %ah,%al
rep nop # todo(jart): interrupts are better
jz 1b
mov %di,%dx
xor %ax,%ax
in %dx,%al
pop %bp
ret
.endfn sgetc,globl
.source __FILE__