在Kernel下使用Debug Card顯示除錯訊息

以echo 5 > /proc/acpi/sleep除錯為例

在drivers/acpi/hardware/hwsleep.c中入紅色字的內容:

#include asm/io.h
acpi_status asmlinkage acpi_enter_sleep_state(u8 sleep_state){

....
status = acpi_hw_register_write(ACPI_MTX_DO_NOT_LOCK,
ACPI_REGISTER_PM1B_CONTROL,
PM1Bcontrol);
if (ACPI_FAILURE(status)) {
return_ACPI_STATUS(status);
}

//Jeff Liao add the 80 port debug msg.
outb((unsigned char)0xff, 0x80);
outb((unsigned char)0xff, 0x80);
acpi_os_stall(100000000);

/* Insert SLP_ENABLE bit */

PM1Acontrol |= sleep_enable_reg_info->access_bit_mask;
PM1Bcontrol |= sleep_enable_reg_info->access_bit_mask;

......
}

其中acpi_os_stall實做如下，該function可以stall kernel執行us (ms)，當us=10 000 000 是代表10 秒

#include linux/nmi.h

void acpi_os_stall(u32 us)
{
while (us) {
u32 delay = 1000;

if (delay > us)
delay = us;
udelay(delay);
touch_nmi_watchdog();
us -= delay;
}