WhyCan Forum(哇酷开发者社区)

1. 内核开启
(1)内核配置
Kernel hacking  --->
    printk and dmesg options  --->
        [* ] Enable dynamic printk() support

2.驱动支持
以 pr_debug / pr_err / pr_warn / pr_info打印的消息
#if defined(CONFIG_DYNAMIC_DEBUG)
// dynamic_pr_debug() uses pr_fmt() internally so we don't need it here
#define pr_debug(fmt, ...) \
         dynamic_pr_debug(fmt, ##__VA_ARGS__)
#elif defined(DEBUG)
#define pr_debug(fmt, ...) \
        printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
#define pr_debug(fmt, ...) \
        no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#endif

3.挂载
mount -t debugfs none /sys/kernel/debug

4.先查看下
cat /sys/kernel/debug/dynamic_debug/control

5.确保printk的打印等级OK
ensure console loglevel value > 7:
cat /proc/sys/kernel/printk
8    4    1    7 //8 is ok
echo 8 > /proc/sys/kernel/printk

6. 使用
1) module
echo 'module xhci_hcd +p' > /sys/kernel/debug/dynamic_debug/control //enable
echo 'module xhci_hcd -p' > /sys/kernel/debug/dynamic_debug/control //disable
 other usb module: 
echo 'module phy +p' > /sys/kernel/debug/dynamic_debug/control
echo 'module udc_core +p' > /sys/kernel/debug/dynamic_debug/control
echo 'module snps_udc_core +p' > /sys/kernel/debug/dynamic_debug/control
echo 'module libcomposite +p' > /sys/kernel/debug/dynamic_debug/control

 2) file
echo 'file hub.c +p' > /sys/kernel/debug/dynamic_debug/control //enable
echo 'file hub.c -p' > /sys/kernel/debug/dynamic_debug/control //disable

3) function
echo 'func hub_event +p' > /sys/kernel/debug/dynamic_debug/control //enable
echo 'func hub_event -p' > /sys/kernel/debug/dynamic_debug/control //disable