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update console.c for more correct comments

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This commit is contained in:
yuchen 2015-03-13 20:38:58 +08:00
parent a5f0ac0511
commit 6770c2a473
1 changed files with 8 additions and 8 deletions
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16
labcodes/lab1/kern/driver/console.c
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@ -65,14 +65,14 @@ static uint16_t addr_6845;
static void
cga_init(void) {
volatile uint16_t *cp = (uint16_t *)CGA_BUF; //CGA_BUF: 0xB8000 (彩色显示的显存物理基址)
uint16_t was = *cp; //保存当前光标所在值
*cp = (uint16_t) 0xA55A;
if (*cp != 0xA55A) {
cp = (uint16_t*)MONO_BUF; //黑白显示的显存基址 MONO_BUF： 0xB0000
addr_6845 = MONO_BASE; //黑白显示控制的IO地址，MONO_BASE: 0x3B4
} else {
*cp = was; //还原原来的光标所在值
addr_6845 = CGA_BASE; // 彩色显示控制的IO地址， CGA_BASE: 0x3D4
uint16_t was = *cp; //保存当前显存0xB8000处的值
*cp = (uint16_t) 0xA55A; // 给这个地址随便写个值，看看能否再读出同样的值
if (*cp != 0xA55A) { // 如果读不出来，说明没有这块显存，即是单显配置
cp = (uint16_t*)MONO_BUF; //设置为单显的显存基址 MONO_BUF： 0xB0000
addr_6845 = MONO_BASE; //设置为单显控制的IO地址，MONO_BASE: 0x3B4
} else { // 如果读出来了，有这块显存，即是彩显配置
*cp = was; //还原原来显存位置的值
addr_6845 = CGA_BASE; // 设置为彩显控制的IO地址，CGA_BASE: 0x3D4
}
// Extract cursor location