Linux Driver Development--__stringify

There is a macro __stringify in the Linux kernel, which is defined in Include/linux/stringify.h as follows:

#ifndef __linux_stringify_h #define __linux_stringify_h/*  Indirect stringification.  Doing levels allows the parameter to be  a * macro itself. */ #define __stringify_1 (x ...)    #x#define __stringify (x ...)    __stringify_1 (x)#endif/    *!__linux_stringify_h */

The effect is actually to convert the x directly to a string. The return value is a string, not a variable name.

Usage 1:

   #define __attr (_name,_mode,_show,_store) {/     = {. Name = __stringify (_name),. Mode = _mode},/ c9/>= _show,     /     = _store,     /    }

Suppose we use __attr this way:

__attr (Var_name, 777, show_function, store_function)

Then, the value that is actually copied to the. Attr.name is "Var_name" instead of the value represented by the Var_name variable.

Usage 2: Convert an enumeration type to a string

#define Wcd_mbhc_stringify (s)  __stringify (s)

enum wcd_notify_event {    wcd_event_invalid,    /**/    wcd_event_pre_ Micbias_2_off,    Wcd_event_post_micbias_2_off,    wcd_event_pre_micbias_2_on,    Wcd_event_post_micbias _2_ON,

Static Const Char*wcd_mbhc_get_event_string (int Event){    Switch(Event) {     CaseWcd_event_pre_micbias_2_off:returnwcd_mbhc_stringify (Wcd_event_pre_micbias_2_off);  CaseWcd_event_post_micbias_2_off:returnwcd_mbhc_stringify (Wcd_event_post_micbias_2_off);  Casewcd_event_pre_micbias_2_on:returnWcd_mbhc_stringify (wcd_event_pre_micbias_2_on);

Linux Driver Development--__stringify