Writing output to the Raspberry Pi console

On to our second kernel module! Here, we shall emit nine printk instances, one at each of the eight log levels, plus one via the pr_devel() macro (which is really nothing but the KERN_DEBUG log level). Let's check out the relevant code:

// ch4/printk_loglvl/printk_loglvl.c
static int __init printk_loglvl_init(void)
{
    pr_emerg ("Hello, world @ log-level KERN_EMERG   [0]\n");
    pr_alert ("Hello, world @ log-level KERN_ALERT   [1]\n");
    pr_crit  ("Hello, world @ log-level KERN_CRIT    [2]\n");
    pr_err   ("Hello, world @ log-level KERN_ERR     [3]\n");
    pr_warn  ("Hello, world @ log-level KERN_WARNING [4]\n");
    pr_notice("Hello, world @ log-level KERN_NOTICE  [5]\n");
    pr_info  ("Hello, world @ log-level KERN_INFO    [6]\n");
    pr_debug ("Hello, world @ log-level KERN_DEBUG   [7]\n");
    pr_devel("Hello, world via the pr_devel() macro&quot...