Where does dev_dbg log?

dev_dbg()

expands to dynamic_dev_dbg()

, dev_printk()

or no-op depending on the compilation flags.

#if defined(CONFIG_DYNAMIC_DEBUG)
#define dev_dbg(dev, format, ...)                    \
do {                                                 \
    dynamic_dev_dbg(dev, format, ##__VA_ARGS__); \
} while (0)
#elif defined(DEBUG)
#define dev_dbg(dev, format, arg...)            \
    dev_printk(KERN_DEBUG, dev, format, ##arg)
#else
#define dev_dbg(dev, format, arg...)                            \
({                                                              \
    if (0)                                                  \
            dev_printk(KERN_DEBUG, dev, format, ##arg);     \
})
#endif

      

        
        
        
      

    

dynamic_dev_dbg()

and the dev_printk()

call dev_printk_emit()

that calls vprintk_emit()

.

This same function is called normally when you are executing only printk()

. Just note that the rest of the functions, such as dev_err()

, will end up in the same function.

Thus, it is obvious that the buffer is the same, that is, the core of the intravenous buffer.

The registered message at the end is printed on

• The current console if the kernel loglevel (can be changed with the kernel command line or via procf) is sufficient for a specific message, here KERN_DEBUG.
• An internal buffer that can be read by executing the command dmesg
  
  .

Note. The data in 2 is retained as long as there is no space in the buffer. Because it is limited and cool, new data is inferior to old data.