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// Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use libc::{gmtime_r, time, time_t, tm};
use std::cmp::min;
use std::mem;
use crate::BusDevice;
const INDEX_MASK: u8 = 0x7f;
const INDEX_OFFSET: u64 = 0x0;
const DATA_OFFSET: u64 = 0x1;
const DATA_LEN: usize = 128;
/// A CMOS/RTC device commonly seen on x86 I/O port 0x70/0x71.
pub struct Cmos {
index: u8,
data: [u8; DATA_LEN],
}
impl Cmos {
/// Constructs a CMOS/RTC device with initial data.
/// `mem_below_4g` is the size of memory in bytes below the 32-bit gap.
/// `mem_above_4g` is the size of memory in bytes above the 32-bit gap.
pub fn new(mem_below_4g: u64, mem_above_4g: u64) -> Cmos {
let mut data = [0u8; DATA_LEN];
// Extended memory from 16 MB to 4 GB in units of 64 KB
let ext_mem = min(
0xFFFF,
mem_below_4g.saturating_sub(16 * 1024 * 1024) / (64 * 1024),
);
data[0x34] = ext_mem as u8;
data[0x35] = (ext_mem >> 8) as u8;
// High memory (> 4GB) in units of 64 KB
let high_mem = min(0xFFFFFF, mem_above_4g / (64 * 1024));
data[0x5b] = high_mem as u8;
data[0x5c] = (high_mem >> 8) as u8;
data[0x5d] = (high_mem >> 16) as u8;
Cmos { index: 0, data }
}
}
impl BusDevice for Cmos {
fn debug_label(&self) -> String {
"cmos".to_owned()
}
fn write(&mut self, offset: u64, data: &[u8]) {
if data.len() != 1 {
return;
}
match offset {
INDEX_OFFSET => self.index = data[0] & INDEX_MASK,
DATA_OFFSET => self.data[self.index as usize] = data[0],
o => panic!("bad write offset on CMOS device: {}", o),
}
}
fn read(&mut self, offset: u64, data: &mut [u8]) {
fn to_bcd(v: u8) -> u8 {
assert!(v < 100);
((v / 10) << 4) | (v % 10)
}
if data.len() != 1 {
return;
}
data[0] = match offset {
INDEX_OFFSET => self.index,
DATA_OFFSET => {
let seconds;
let minutes;
let hours;
let week_day;
let day;
let month;
let year;
// The time and gmtime_r calls are safe as long as the structs they are given are
// large enough, and neither of them fail. It is safe to zero initialize the tm
// struct because it contains only plain data.
unsafe {
let mut tm: tm = mem::zeroed();
let mut now: time_t = 0;
time(&mut now as *mut _);
gmtime_r(&now, &mut tm as *mut _);
// The following lines of code are safe but depend on tm being in scope.
seconds = tm.tm_sec;
minutes = tm.tm_min;
hours = tm.tm_hour;
week_day = tm.tm_wday + 1;
day = tm.tm_mday;
month = tm.tm_mon + 1;
year = tm.tm_year;
};
match self.index {
0x00 => to_bcd(seconds as u8),
0x02 => to_bcd(minutes as u8),
0x04 => to_bcd(hours as u8),
0x06 => to_bcd(week_day as u8),
0x07 => to_bcd(day as u8),
0x08 => to_bcd(month as u8),
0x09 => to_bcd((year % 100) as u8),
0x32 => to_bcd(((year + 1900) / 100) as u8),
_ => {
// self.index is always guaranteed to be in range via INDEX_MASK.
self.data[(self.index & INDEX_MASK) as usize]
}
}
}
o => panic!("bad read offset on CMOS device: {}", o),
}
}
}
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