/* * skull.c -- sample typeless module. * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files.  The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates.   No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * BUGS: *   -it only runs on intel platforms. *   -readb() should be used (see short.c): skull doesn't work with 2.1 * */#ifndef __KERNEL__#  define __KERNEL__#endif#ifndef MODULE#  define MODULE#endif#ifndef EXPORT_SYMTAB#  define EXPORT_SYMTAB#endif#include <linux/config.h>#include <linux/module.h>#include <linux/kernel.h> /* printk */#include <linux/ioport.h>#include <linux/errno.h>#include <asm/system.h> /* cli(), *_flags */#include <linux/mm.h> /* vremap (2.0) */#include <asm/io.h> /* ioremap */#include "sysdep.h"/* The region we look at. */#define ISA_REGION_BEGIN 0xA0000#define ISA_REGION_END   0x100000#define STEP 2048/* have three symbols to export */       void skull_fn1(void){}static void skull_fn2(void){}       int  skull_variable;#ifndef __USE_OLD_SYMTAB__EXPORT_SYMBOL (skull_fn1);EXPORT_SYMBOL (skull_fn2);EXPORT_SYMBOL (skull_variable);#endifstatic int skull_register(void) /* and export them */{#ifdef __USE_OLD_SYMTAB__  static struct symbol_table skull_syms = {#include <linux/symtab_begin.h>        X(skull_fn1),        X(skull_fn2),        X(skull_variable),#include <linux/symtab_end.h>	};  register_symtab(&skull_syms);#endif   /* __USE_OLD_SYMTAB__ */  return 0;}/* perform hardware autodetection */int skull_probe_hw(unsigned int port, unsigned int range){   /* do smart probing here */   return -1; /* not found  :-) */}/* perform hardware initalizazion */int skull_init_board(unsigned int port){  /* do smart initalization here */  return 0; /* done :-) */}/* detect the the device if the region is still free */static int skull_detect(unsigned int port, unsigned int range){    int err;    if ((err = check_region(port,range)) < 0) return err; /* busy */    if (skull_probe_hw(port,range) != 0) return -ENODEV;  /* not found */    request_region(port,range,"skull");                   /* "Can't fail" */    return 0;}/* * port ranges: the device can reside between * 0x280 and 0x300, in step of 0x10. It uses 0x10 ports. */#define SKULL_PORT_FLOOR 0x280#define SKULL_PORT_CEIL  0x300#define SKULL_PORT_RANGE  0x010/* * the following function performs autodetection, unless a specific * value was assigned by insmod to "skull_port_base" */static int skull_port_base=0; /* 0 forces autodetection */MODULE_PARM (skull_port_base, "i");MODULE_PARM_DESC (skull_port_base, "Base I/O port for skull");static int skull_find_hw(void) /* returns the # of devices */{    /* base is either the load-time value or the first trial */    int base = skull_port_base ? skull_port_base                              : SKULL_PORT_FLOOR;     int result = 0;    /* loop one time if value assigned, try them all if autodetecting */    do {	if (skull_detect(base, SKULL_PORT_RANGE) == 0) {	    skull_init_board(base);	    result++;	}	base += SKULL_PORT_RANGE; /* prepare for next trial */    }    while (skull_port_base == 0 && base < SKULL_PORT_CEIL);    return result;}int skull_init(void){    /*     * Print the isa region map, in blocks of 2K bytes.     * This is not the best code, as it prints too many lines,     * but it deserves to remain short to be included in the book.     * Note also that read() should be used instead of pointers.     */    unsigned char oldval, newval; /* values read from memory   */    unsigned long flags;          /* used to hold system flags */    unsigned long add, i;    void *base;        /* Use ioremap to get a handle on our region */    base = ioremap(ISA_REGION_BEGIN, ISA_REGION_END - ISA_REGION_BEGIN);    base -= ISA_REGION_BEGIN;  /* Do the offset once */        /* probe all the memory hole in 2KB steps */    for (add = ISA_REGION_BEGIN; add < ISA_REGION_END; add += STEP) {	/*	 * Check for an already allocated region.	 */	if (check_mem_region (add, 2048)) {		printk(KERN_INFO "%lx: Allocated\n", add);		continue;	}	/*	 * Read and write the beginning of the region and see what happens.	 */	save_flags(flags); 	cli();	oldval = readb (base + add);  /* Read a byte */	writeb (oldval^0xff, base + add);	mb();	newval = readb (base + add);	writeb (oldval, base + add);	restore_flags(flags);	if ((oldval^newval) == 0xff) {  /* we re-read our change: it's ram */	    printk(KERN_INFO "%lx: RAM\n", add);	    continue;	}	if ((oldval^newval) != 0) {  /* random bits changed: it's empty */	    printk(KERN_INFO "%lx: empty\n", add);	    continue;	}		/*	 * Expansion rom (executed at boot time by the bios)	 * has a signature where the first byt is 0x55, the second 0xaa,	 * and the third byte indicates the size of such rom	 */	if ( (oldval == 0x55) && (readb (base + add + 1) == 0xaa)) {	    int size = 512 * readb (base + add + 2);	    printk(KERN_INFO "%lx: Expansion ROM, %i bytes\n",                   add, size);	    add += (size & ~2048) - 2048; /* skip it */	    continue;	}		/*	 * If the tests above failed, we still don't know if it is ROM or	 * empty. Since empty memory can appear as 0x00, 0xff, or the low	 * address byte, we must probe multiple bytes: if at least one of	 * them is different from these three values, then this is rom	 * (though not boot rom).	 */	printk(KERN_INFO "%lx: ", add);	for (i=0; i<5; i++) {	    unsigned long radd = add + 57*(i+1);  /* a "random" value */	    unsigned char val = readb (base + radd);	    if (val && val != 0xFF && val != ((unsigned long) radd&0xFF))		break;	}    	printk("%s\n", i==5 ? "empty" : "ROM");    }    /*     * Find you hardware      */    skull_find_hw();    /*     * Always fail to load (or suceed).     */    skull_register(); /* register your symbol table */    return 0;}module_init(skull_init);