Trying out the dynamic debug_level procfs control

First, let's check out the "driver context" data structure that we shall use throughout this chapter (in fact, we first used it in the previous chapter):

// ch2/procfs_simple_intf/procfs_simple_intf.c
[ ... ]
/* Borrowed from ch1; the 'driver context' data structure;
 * all relevant 'state info' reg the driver and (fictional) 'device'
 * is maintained here.
 */
struct drv_ctx {
    int tx, rx, err, myword, power;
    u32 config1; /* treated as equivalent to 'debug level' of our driver */
    u32 config2;
    u64 config3;
#define MAXBYTES   128
    char oursecret[MAXBYTES];
};
static struct drv_ctx *gdrvctx;
static int debug_level;    /* 'off' (0) by default ... */

Here, we can also see that we have a global integer named debug_level; this will provide dynamic control over the debug verbosity of the "project". The debug level is assigned a range of [0-2], where we have the following...