MTD Partition除了在code中寫死以外，其實還可以透過一些parsers來作規劃，這一章就要來教大家如何使用"Command line partition table parsing"。首先必須在kernel中啟用"Command line partition table parsing"，請參照下圖。
這樣kernel就可以支援"Command line partition table parsing"，然後我們還是拿mtdram.c的code來改（紅色的部份）。
/*
* mtdram - a test mtd device
* Author: Alexander Larsson <alex@cendio.se>
*
* Copyright (c) 1999 Alexander Larsson alex@cendio.se>
* Copyright (c) 2005 Joern Engel <joern@wh.fh-wedel.de>
*
* This code is GPL
*
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/mtd/compatmac.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/mtdram.h>
#include <linux/mtd/partitions.h>
static unsigned long total_size = CONFIG_MTDRAM_TOTAL_SIZE;
static unsigned long erase_size = CONFIG_MTDRAM_ERASE_SIZE;
#define MTDRAM_TOTAL_SIZE (total_size * 1024)
#define MTDRAM_ERASE_SIZE (erase_size * 1024)
#ifdef MODULE
module_param(total_size, ulong, 0);
MODULE_PARM_DESC(total_size, "Total device size in KiB");
module_param(erase_size, ulong, 0);
MODULE_PARM_DESC(erase_size, "Device erase block size in KiB");
#endif
// We could store these in the mtd structure, but we only support 1 device..
static struct mtd_info *mtd_info;
static char partitioned = 0;
static int ram_erase(struct mtd_info *mtd, struct erase_info *instr)
{
if (instr->addr + instr->len > mtd->size)
return -EINVAL;
memset((char *)mtd->priv + instr->addr, 0xff, instr->len);
instr->state = MTD_ERASE_DONE;
mtd_erase_callback(instr);
return 0;
}
static int ram_point(struct mtd_info *mtd, loff_t from, size_t len,
size_t *retlen, void **virt, resource_size_t *phys)
{
if (from + len > mtd->size)
return -EINVAL;
/* can we return a physical address with this driver? */
if (phys)
return -EINVAL;
*virt = mtd->priv + from;
*retlen = len;
return 0;
}
static void ram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
{
}
/*
* Allow NOMMU mmap() to directly map the device (if not NULL)
* - return the address to which the offset maps
* - return -ENOSYS to indicate refusal to do the mapping
*/
static unsigned long ram_get_unmapped_area(struct mtd_info *mtd,
unsigned long len,
unsigned long offset,
unsigned long flags)
{
return (unsigned long) mtd->priv + offset;
}
static int ram_read(struct mtd_info *mtd, loff_t from, size_t len,
size_t *retlen, u_char *buf)
{
if (from + len > mtd->size)
return -EINVAL;
memcpy(buf, mtd->priv + from, len);
*retlen = len;
return 0;
}
static int ram_write(struct mtd_info *mtd, loff_t to, size_t len,
size_t *retlen, const u_char *buf)
{
if (to + len > mtd->size)
return -EINVAL;
memcpy((char *)mtd->priv + to, buf, len);
*retlen = len;
return 0;
}
static void __exit cleanup_mtdram(void)
{
if (mtd_info) {
if (mtd_has_partitions() && partitioned) {
del_mtd_partitions(mtd_info);
} else {
del_mtd_device(mtd_info);
}
vfree(mtd_info->priv);
kfree(mtd_info);
}
}
int mtdram_init_device(struct mtd_info *mtd, void *mapped_address,
unsigned long size, char *name)
{
memset(mtd, 0, sizeof(*mtd));
/* Setup the MTD structure */
mtd->name = name;
mtd->type = MTD_RAM;
mtd->flags = MTD_CAP_RAM;
mtd->size = size;
mtd->writesize = 1;
mtd->erasesize = MTDRAM_ERASE_SIZE;
mtd->priv = mapped_address;
mtd->owner = THIS_MODULE;
mtd->erase = ram_erase;
mtd->point = ram_point;
mtd->unpoint = ram_unpoint;
mtd->get_unmapped_area = ram_get_unmapped_area;
mtd->read = ram_read;
mtd->write = ram_write;
if (mtd_has_partitions()) {
struct mtd_partition *mtd_parts = NULL;
static const char *probes[] =
{ "cmdlinepart", NULL };
int nb_parts = 0;
printk("has partitions\n");
if (mtd_has_cmdlinepart()) {
printk("has probs\n");
nb_parts = parse_mtd_partitions(mtd, probes, &mtd_parts, 0);
}
if (nb_parts > 0) {
printk("partitioned\n");
partitioned = 1;
return add_mtd_partitions(mtd, mtd_parts, nb_parts);
}
}
if (add_mtd_device(mtd)) {
return -EIO;
}
return 0;
}
static int __init init_mtdram(void)
{
void *addr;
int err;
if (!total_size)
return -EINVAL;
/* Allocate some memory */
mtd_info = kmalloc(sizeof(struct mtd_info), GFP_KERNEL);
if (!mtd_info)
return -ENOMEM;
addr = vmalloc(MTDRAM_TOTAL_SIZE);
if (!addr) {
kfree(mtd_info);
mtd_info = NULL;
return -ENOMEM;
}
err = mtdram_init_device(mtd_info,
addr, MTDRAM_TOTAL_SIZE, "brook_flash");
if (err) {
vfree(addr);
kfree(mtd_info);
mtd_info = NULL;
return err;
}
memset(mtd_info->priv, 0xff, MTDRAM_TOTAL_SIZE);
return err;
}
module_init(init_mtdram);
module_exit(cleanup_mtdram);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alexander Larsson <alexl@redhat.com>");
MODULE_DESCRIPTION("Simulated MTD driver for testing");
