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DEFINITIONS
This source file includes following definitions.
- skull_fn1
- skull_fn2
- skull_probe_hw
- skull_init_board
- skull_detect
- skull_find_hw
- skull_init
/*
* 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
*
*/
/* jc: cleaned up, but not yet run for anything */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.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 */
/* 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;
EXPORT_SYMBOL (skull_fn1);
EXPORT_SYMBOL (skull_fn2);
EXPORT_SYMBOL (skull_variable);
/* 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_param(skull_port_base, int, 0);
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).
*/
return 0;
}
module_init(skull_init);