Linux内核中platform驱动模型架构与dm9000网卡驱动移植
转自http://blog.csdn.net/yinwei520/article/details/6262931
一、硬件链接情况
DM9000在电路板上的连接中与编程相关的如下：
1)EECS拉高：16bit模式；
2)INT连接到2440 EINT18：INT脚为低时为有效中断信号，中断线为EINT18
3)cs连接到2440的nGCS4，CMD连接2440地址总线ADDR[2]：知道上面这些信息已经足够移植驱动了。
二、platform驱动模型
从Linux 2.6起引入了一套新的驱动管理和注册机制:Platform_device和Platform_driver。Linux中大部分的设备驱动，都可以使用这套机制, 设备用Platform_device表示，驱动用Platform_driver进行注册。
Linux platform driver机制和传统的device driver 机制(通过driver_register函数进行注册)相比，一个十分明显的优势在于platform机制将设备本身的资源注册进内核，由内核统一管理，在驱动程序中使用这些资源时通过platform device提供的标准接口进行申请并使用。这样提高了驱动和资源管理的独立性，并且拥有较好的可移植性和安全性(这些标准接口是安全的)。
Platform机制的本身使用并不复杂，由两部分组成：platform_device和platfrom_driver。通过Platform机制开发发底层驱动的大致流程为: 定义 platform_device à 注册 platform_device à 定义 platform_driver à注册 platform_driver。
首先要确认的就是设备的资源信息，例如设备的地址，中断号等。
在2.6内核中platform设备用结构体platform_device来描述，该结构体定义在kernel/include/linux/platform_device.h中，
struct platform_device {
const char * name;
u32 id;
struct device dev;
u32 num_resources;
struct resource * resource;
};
该结构一个重要的元素是resource，该元素存入了最为重要的设备资源信息，定义在kernel/include/linux/ioport.h中，
struct resource {
const char *name;
unsigned long start, end;
unsigned long flags;
struct resource *parent, *sibling, *child;
};
一个独立的挂接在cpu总线上的设备单元,一般都需要一段线性的地址空间来描述设备自身,linux是怎么管理所有的这些外部"物理地址范围段",进而给用户和linux自身一个比较好的观察4G总线上挂接的一个个设备实体的简洁、统一级联视图的呢?
linux采用struct resource结构体来描述一个挂接在cpu总线上的设备实体(32位cpu的总线地址范围是0~4G):
resource->start描述设备实体在cpu总线上的线性起始物理地址;
resource->end -描述设备实体在cpu总线上的线性结尾物理地址;
resource->name 描述这个设备实体的名称,这个名字开发人员可以随意起,但最好贴切;
resource->flag 描述这个设备实体的一些共性和特性的标志位;
问题:我怎样知道设备实体在cpu总线上的线性起始物理地址跟线性结尾物理地址？
通过查看原理图吗？？如果是，那具体应该怎样分析呢？
三、现在分析dm9000在Linux内核中的结构。
static struct platform_device与static struct platform_resources结构体在arch/arm/plat-s3c24xx/devs.c中定义，在arch/arm/plat-s3c/include/plat/devs.h中声明，在arch/arm/mach-s3c2440/mach-smdk2440.c中使用（通过函数：platform_add_devices()注册进内核）。
至于platform_driver的实现就是在dm900.c中实现了。
四、移植
从上图可以看出
a. dm9000的访问地址为BANK4的基址（也许是通过上面的nGCS4看出来的）。（这个我是不明白的）
b. 只有一根地址线ADDR2。
c. 总线位宽为16位，有nWAIT信号。
d. 使用中断引脚为EINT18（使用LAN_INT实现的）。
一 增加DM9000平台设备
增加平台设备前首先要先定义该平台设备，这主要修改arch/arm/plat-s3c24xx/devs.c文件。
1.添加头文件 ，在devs.c文件的头文件引入处添加如下代码：
#include <linux/dm9000.h>
2.定义dm9000平台资源 ，在devs.c文件的合适处添加如下代码（其实看一下源文件就知道合适的意思）：
1. /* DM9000 */
2. static struct resource s3c_dm9k_resource[] = {
3. [0] = {
4. .start = S3C2410_CS4,
5. .end = S3C2410_CS4 + 3,
6. .flags = IORESOURCE_MEM,
7. },
8. [1] = {
9. .start = S3C2410_CS4 + 4,
10. .end = S3C2410_CS4 + 4 + 3,
11. .flags = IORESOURCE_MEM,
12. },
13. [2] = {
14. .start = IRQ_EINT7,
15. .end = IRQ_EINT7,
16. .flags = IORESOURCE_IRQ | IRQF_TRIGGER_RISING,
17. }
18.
19. };
20.
21. /* for the moment we limit ourselves to 16bit IO until some
22. * better IO routines can be written and tested
23. */
24.
25. static struct dm9000_plat_data s3c_dm9k_platdata = {
26. .flags = DM9000_PLATF_16BITONLY,
27. };
28.
29. struct platform_device s3c_device_dm9k = {
30. .name = "dm9000",
31. .id = 0,
32. .num_resources = ARRAY_SIZE(s3c_dm9k_resource),
33. .resource = s3c_dm9k_resource,
34. .dev = {
35. .platform_data = &s3c_dm9k_platdata,
36. }
37. };
38.
39. EXPORT_SYMBOL(s3c_device_dm9k);
NOTE:
a.s3c_dm9k_resource数组定义了3个资源：两个内存空间和一个中断号。数组项0、1定义了访问dm9000时使用的地址。在dm9000的芯片手册上有如下的介绍：
CMD Command Type
When high, the access of this command cycle is DATA port
When low, the access of this command cycle is ADDRESS port
所以数组项0、1的.start域就容易理解了，S3C2410_CS4中addr2为0，表示传输地址；S3C2410_CS4 + 4中addr2为1，表示传输数据。数组项[2]定义的中断号就较容易理解。
b.结构s3c_dm9k_platdata中指定了数据总线宽度为16。
c.结构s3c_device_dm9k就是dm9000的平台设备，其中.resource和.dev项分别指向前面定义的s3c_dm9k_resource和s3c_dm9k_platdata。
3.把定义的平台设备加入到内核设备列表中 ，在common-smdk.c文件的smdk_devs数组中添加一下代码：(我的为mach-mini2440.c文件mini2440_devices数组)
&s3c_device_dm9k,
这样，系统启动时就会把这个数组中的设备注册到内核中。
二 修改dm9000.c文件
对dm9000的枚举最终由dm9000_probe函数来实现。
1.添加头文件 ，在dm9000.c的头文件引入处增加以下代码，定义了一些寄存器的宏定义：
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#if defined(CONFIG_ARCH_S3C2410)
#include <mach/regs-mem.h>
#endif
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#if defined(CONFIG_ARCH_S3C2410)
#include <mach/regs-mem.h>
#endif
#if defined(CONFIG_ARCH_S3C2410)
#include <mach/regs-mem.h>
#endif
2.修改probe函数 ，通过设置存储控制器使BANK4可用，修改后的dm9000_probe函数如下，其中修改的地方都由CONFIG_ARCH_S3C2410包括：
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# *
# * Search DM9000 board, allocate space and register it
# */
# static int __devinit
# dm9000_probe(struct platform_device *pdev)
# {
# struct dm9000_plat_data *pdata = pdev->dev.platform_data;
# struct board_info *db; /* Point a board information structure */
# struct net_device *ndev;
# const unsigned char *mac_src;
# int ret = 0;
# int iosize;
# int i;
# u32 id_val;
#
# # if defined(CONFIG_ARCH_S3C2410)
# unsigned int oldval_bwscon = *(volatile unsigned int *)S3C2410_BWSCON;
# unsigned int oldval_bankcon4 = *(volatile unsigned int *)S3C2410_BANKCON4;
# # endif
#
# /* Init network device */
# ndev = alloc_etherdev(sizeof(struct board_info));
# if (!ndev) {
# dev_err(&pdev->dev, "could not allocate device./n");
# return -ENOMEM;
# }
#
# SET_NETDEV_DEV(ndev, &pdev->dev);
#
# dev_dbg(&pdev->dev, "dm9000_probe()/n");
#
# #if defined(CONFIG_ARCH_S3C2410)
# *((volatile unsigned int *)S3C2410_BWSCON) =
# (oldval_bwscon & ~(3<<16)) | S3C2410_BWSCON_DW4_16 | S3C2410_BWSCON_WS4 | S3C2410_BWSCON_ST4;
# *((volatile unsigned int *)S3C2410_BANKCON4) = 0x1f7c;
# #endif
#
# /* setup board info structure */
# db = netdev_priv(ndev);
# memset(db, 0, sizeof(*db));
#
# db->dev = &pdev->dev;
# db->ndev = ndev;
#
# spin_lock_init(&db->lock);
# mutex_init(&db->addr_lock);
#
# INIT_DELAYED_WORK(&db->phy_poll, dm9000_poll_work);
#
# db->addr_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
# db->data_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
# db->irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
#
# if (db->addr_res == NULL || db->data_res == NULL ||
# db->irq_res == NULL) {
# dev_err(db->dev, "insufficient resources/n");
# ret = -ENOENT;
# goto out;
# }
#
# iosize = res_size(db->addr_res);
# db->addr_req = request_mem_region(db->addr_res->start, iosize,
# pdev->name);
#
# if (db->addr_req == NULL) {
# dev_err(db->dev, "cannot claim address reg area/n");
# ret = -EIO;
# goto out;
# }
#
# db->io_addr = ioremap(db->addr_res->start, iosize);
#
# if (db->io_addr == NULL) {
# dev_err(db->dev, "failed to ioremap address reg/n");
# ret = -EINVAL;
# goto out;
# }
#
# iosize = res_size(db->data_res);
# db->data_req = request_mem_region(db->data_res->start, iosize,
# pdev->name);
#
# if (db->data_req == NULL) {
# dev_err(db->dev, "cannot claim data reg area/n");
# ret = -EIO;
# goto out;
# }
#
# db->io_data = ioremap(db->data_res->start, iosize);
#
# if (db->io_data == NULL) {
# dev_err(db->dev, "failed to ioremap data reg/n");
# ret = -EINVAL;
# goto out;
# }
#
# /* fill in parameters for net-dev structure */
# ndev->base_addr = (unsigned long)db->io_addr;
# ndev->irq = db->irq_res->start;
#
# /* ensure at least we have a default set of IO routines */
# dm9000_set_io(db, iosize);
#
# /* check to see if anything is being over-ridden */
# if (pdata != NULL) {
# /* check to see if the driver wants to over-ride the
# * default IO width */
#
# if (pdata->flags & DM9000_PLATF_8BITONLY)
# dm9000_set_io(db, 1);
#
# if (pdata->flags & DM9000_PLATF_16BITONLY)
# dm9000_set_io(db, 2);
#
# if (pdata->flags & DM9000_PLATF_32BITONLY)
# dm9000_set_io(db, 4);
#
# /* check to see if there are any IO routine
# * over-rides */
#
# if (pdata->inblk != NULL)
# db->inblk = pdata->inblk;
#
# if (pdata->outblk != NULL)
# db->outblk = pdata->outblk;
#
# if (pdata->dumpblk != NULL)
# db->dumpblk = pdata->dumpblk;
#
# db->flags = pdata->flags;
# }
#
# #ifdef CONFIG_DM9000_FORCE_SIMPLE_PHY_POLL
# db->flags |= DM9000_PLATF_SIMPLE_PHY;
# #endif
#
# dm9000_reset(db);
#
# /* try multiple times, DM9000 sometimes gets the read wrong */
# for (i = 0; i < 8; i++) {
# id_val = ior(db, DM9000_VIDL);
# id_val |= (u32)ior(db, DM9000_VIDH) << 8;
# id_val |= (u32)ior(db, DM9000_PIDL) << 16;
# id_val |= (u32)ior(db, DM9000_PIDH) << 24;
#
# if (id_val == DM9000_ID)
# break;
# dev_err(db->dev, "read wrong id 0x%08x/n", id_val);
# }
#
# if (id_val != DM9000_ID) {
# dev_err(db->dev, "wrong id: 0x%08x/n", id_val);
# ret = -ENODEV;
# goto out;
# }
#
# /* Identify what type of DM9000 we are working on */
#
# id_val = ior(db, DM9000_CHIPR);
# dev_dbg(db->dev, "dm9000 revision 0x%02x/n", id_val);
#
# switch (id_val) {
# case CHIPR_DM9000A:
# db->type = TYPE_DM9000A;
# break;
# case CHIPR_DM9000B:
# db->type = TYPE_DM9000B;
# break;
# default:
# dev_dbg(db->dev, "ID %02x => defaulting to DM9000E/n", id_val);
# db->type = TYPE_DM9000E;
# }
#
# /* from this point we assume that we have found a DM9000 */
#
# /* driver system function */
# ether_setup(ndev);
#
# ndev->open = &dm9000_open;
# ndev->hard_start_xmit = &dm9000_start_xmit;
# ndev->tx_timeout = &dm9000_timeout;
# ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
# ndev->stop = &dm9000_stop;
# ndev->set_multicast_list = &dm9000_hash_table;
# ndev->ethtool_ops = &dm9000_ethtool_ops;
# ndev->do_ioctl = &dm9000_ioctl;
#
# #ifdef CONFIG_NET_POLL_CONTROLLER
# ndev->poll_controller = &dm9000_poll_controller;
# #endif
#
# db->msg_enable = NETIF_MSG_LINK;
# db->mii.phy_id_mask = 0x1f;
# db->mii.reg_num_mask = 0x1f;
# db->mii.force_media = 0;
# db->mii.full_duplex = 0;
# db->mii.dev = ndev;
# db->mii.mdio_read = dm9000_phy_read;
# db->mii.mdio_write = dm9000_phy_write;
#
# #if defined(CONFIG_ARCH_S3C2410)
# printk("Now use the default MAC address: 08:90:90:90:90:90/n");
# mac_src = "friendly-arm";
# ndev->dev_addr[0] = 0x08;
# ndev->dev_addr[1] = 0x90;
# ndev->dev_addr[2] = 0x90;
# ndev->dev_addr[3] = 0x90;
# ndev->dev_addr[4] = 0x90;
# ndev->dev_addr[5] = 0x90;
# #else
# mac_src = "eeprom";
#
# /* try reading the node address from the attached EEPROM */
# for (i = 0; i < 6; i += 2)
# dm9000_read_eeprom(db, i / 2, ndev->dev_addr+i);
#
# if (!is_valid_ether_addr(ndev->dev_addr) && pdata != NULL) {
# mac_src = "platform data";
# memcpy(ndev->dev_addr, pdata->dev_addr, 6);
# }
#
# if (!is_valid_ether_addr(ndev->dev_addr)) {
# /* try reading from mac */
#
# mac_src = "chip";
# for (i = 0; i < 6; i++)
# ndev->dev_addr[i] = ior(db, i+DM9000_PAR);
# }
#
# if (!is_valid_ether_addr(ndev->dev_addr))
# dev_warn(db->dev, "%s: Invalid ethernet MAC address. Please "
# "set using ifconfig/n", ndev->name);
# #endif
#
# platform_set_drvdata(pdev, ndev);
# ret = register_netdev(ndev);
#
# if (ret == 0)
# printk(KERN_INFO "%s: dm9000%c at %p,%p IRQ %d MAC: %pM (%s)/n",
# ndev->name, dm9000_type_to_char(db->type),
# db->io_addr, db->io_data, ndev->irq,
# ndev->dev_addr, mac_src);
# return 0;
#
# out:
# #if defined(CONFIG_ARCH_S3C2410)
# *(volatile unsigned int *)S3C2410_BWSCON = oldval_bwscon;
# *(volatile unsigned int *)S3C2410_BANKCON4 = oldval_bankcon4;
# #endif
# dev_err(db->dev, "not found (%d)./n", ret);
#
# dm9000_release_board(pdev, db);
# free_netdev(ndev);
#
# return ret;
# }
# *
# * Search DM9000 board, allocate space and register it
# */
# static int __devinit
# dm9000_probe(struct platform_device *pdev)
# {
# struct dm9000_plat_data *pdata = pdev->dev.platform_data;
# struct board_info *db; /* Point a board information structure */
# struct net_device *ndev;
# const unsigned char *mac_src;
# int ret = 0;
# int iosize;
# int i;
# u32 id_val;
#
# # if defined(CONFIG_ARCH_S3C2410)
# unsigned int oldval_bwscon = *(volatile unsigned int *)S3C2410_BWSCON;
# unsigned int oldval_bankcon4 = *(volatile unsigned int *)S3C2410_BANKCON4;
# # endif
#
# /* Init network device */
# ndev = alloc_etherdev(sizeof(struct board_info));
# if (!ndev) {
# dev_err(&pdev->dev, "could not allocate device./n");
# return -ENOMEM;
# }
#
# SET_NETDEV_DEV(ndev, &pdev->dev);
#
# dev_dbg(&pdev->dev, "dm9000_probe()/n");
#
# #if defined(CONFIG_ARCH_S3C2410)
# *((volatile unsigned int *)S3C2410_BWSCON) =
# (oldval_bwscon & ~(3<<16)) | S3C2410_BWSCON_DW4_16 | S3C2410_BWSCON_WS4 | S3C2410_BWSCON_ST4;
# *((volatile unsigned int *)S3C2410_BANKCON4) = 0x1f7c;
# #endif
#
# /* setup board info structure */
# db = netdev_priv(ndev);
# memset(db, 0, sizeof(*db));
#
# db->dev = &pdev->dev;
# db->ndev = ndev;
#
# spin_lock_init(&db->lock);
# mutex_init(&db->addr_lock);
#
# INIT_DELAYED_WORK(&db->phy_poll, dm9000_poll_work);
#
# db->addr_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
# db->data_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
# db->irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
#
# if (db->addr_res == NULL || db->data_res == NULL ||
# db->irq_res == NULL) {
# dev_err(db->dev, "insufficient resources/n");
# ret = -ENOENT;
# goto out;
# }
#
# iosize = res_size(db->addr_res);
# db->addr_req = request_mem_region(db->addr_res->start, iosize,
# pdev->name);
#
# if (db->addr_req == NULL) {
# dev_err(db->dev, "cannot claim address reg area/n");
# ret = -EIO;
# goto out;
# }
#
# db->io_addr = ioremap(db->addr_res->start, iosize);
#
# if (db->io_addr == NULL) {
# dev_err(db->dev, "failed to ioremap address reg/n");
# ret = -EINVAL;
# goto out;
# }
#
# iosize = res_size(db->data_res);
# db->data_req = request_mem_region(db->data_res->start, iosize,
# pdev->name);
#
# if (db->data_req == NULL) {
# dev_err(db->dev, "cannot claim data reg area/n");
# ret = -EIO;
# goto out;
# }
#
# db->io_data = ioremap(db->data_res->start, iosize);
#
# if (db->io_data == NULL) {
# dev_err(db->dev, "failed to ioremap data reg/n");
# ret = -EINVAL;
# goto out;
# }
#
# /* fill in parameters for net-dev structure */
# ndev->base_addr = (unsigned long)db->io_addr;
# ndev->irq = db->irq_res->start;
#
# /* ensure at least we have a default set of IO routines */
# dm9000_set_io(db, iosize);
#
# /* check to see if anything is being over-ridden */
# if (pdata != NULL) {
# /* check to see if the driver wants to over-ride the
# * default IO width */
#
# if (pdata->flags & DM9000_PLATF_8BITONLY)
# dm9000_set_io(db, 1);
#
# if (pdata->flags & DM9000_PLATF_16BITONLY)
# dm9000_set_io(db, 2);
#
# if (pdata->flags & DM9000_PLATF_32BITONLY)
# dm9000_set_io(db, 4);
#
# /* check to see if there are any IO routine
# * over-rides */
#
# if (pdata->inblk != NULL)
# db->inblk = pdata->inblk;
#
# if (pdata->outblk != NULL)
# db->outblk = pdata->outblk;
#
# if (pdata->dumpblk != NULL)
# db->dumpblk = pdata->dumpblk;
#
# db->flags = pdata->flags;
# }
#
# #ifdef CONFIG_DM9000_FORCE_SIMPLE_PHY_POLL
# db->flags |= DM9000_PLATF_SIMPLE_PHY;
# #endif
#
# dm9000_reset(db);
#
# /* try multiple times, DM9000 sometimes gets the read wrong */
# for (i = 0; i < 8; i++) {
# id_val = ior(db, DM9000_VIDL);
# id_val |= (u32)ior(db, DM9000_VIDH) << 8;
# id_val |= (u32)ior(db, DM9000_PIDL) << 16;
# id_val |= (u32)ior(db, DM9000_PIDH) << 24;
#
# if (id_val == DM9000_ID)
# break;
# dev_err(db->dev, "read wrong id 0x%08x/n", id_val);
# }
#
# if (id_val != DM9000_ID) {
# dev_err(db->dev, "wrong id: 0x%08x/n", id_val);
# ret = -ENODEV;
# goto out;
# }
#
# /* Identify what type of DM9000 we are working on */
#
# id_val = ior(db, DM9000_CHIPR);
# dev_dbg(db->dev, "dm9000 revision 0x%02x/n", id_val);
#
# switch (id_val) {
# case CHIPR_DM9000A:
# db->type = TYPE_DM9000A;
# break;
# case CHIPR_DM9000B:
# db->type = TYPE_DM9000B;
# break;
# default:
# dev_dbg(db->dev, "ID %02x => defaulting to DM9000E/n", id_val);
# db->type = TYPE_DM9000E;
# }
#
# /* from this point we assume that we have found a DM9000 */
#
# /* driver system function */
# ether_setup(ndev);
#
# ndev->open = &dm9000_open;
# ndev->hard_start_xmit = &dm9000_start_xmit;
# ndev->tx_timeout = &dm9000_timeout;
# ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
# ndev->stop = &dm9000_stop;
# ndev->set_multicast_list = &dm9000_hash_table;
# ndev->ethtool_ops = &dm9000_ethtool_ops;
# ndev->do_ioctl = &dm9000_ioctl;
#
# #ifdef CONFIG_NET_POLL_CONTROLLER
# ndev->poll_controller = &dm9000_poll_controller;
# #endif
#
# db->msg_enable = NETIF_MSG_LINK;
# db->mii.phy_id_mask = 0x1f;
# db->mii.reg_num_mask = 0x1f;
# db->mii.force_media = 0;
# db->mii.full_duplex = 0;
# db->mii.dev = ndev;
# db->mii.mdio_read = dm9000_phy_read;
# db->mii.mdio_write = dm9000_phy_write;
#
# #if defined(CONFIG_ARCH_S3C2410)
# printk("Now use the default MAC address: 08:90:90:90:90:90/n");
# mac_src = "friendly-arm";
# ndev->dev_addr[0] = 0x08;
# ndev->dev_addr[1] = 0x90;
# ndev->dev_addr[2] = 0x90;
# ndev->dev_addr[3] = 0x90;
# ndev->dev_addr[4] = 0x90;
# ndev->dev_addr[5] = 0x90;
# #else
# mac_src = "eeprom";
#
# /* try reading the node address from the attached EEPROM */
# for (i = 0; i < 6; i += 2)
# dm9000_read_eeprom(db, i / 2, ndev->dev_addr+i);
#
# if (!is_valid_ether_addr(ndev->dev_addr) && pdata != NULL) {
# mac_src = "platform data";
# memcpy(ndev->dev_addr, pdata->dev_addr, 6);
# }
#
# if (!is_valid_ether_addr(ndev->dev_addr)) {
# /* try reading from mac */
#
# mac_src = "chip";
# for (i = 0; i < 6; i++)
# ndev->dev_addr[i] = ior(db, i+DM9000_PAR);
# }
#
# if (!is_valid_ether_addr(ndev->dev_addr))
# dev_warn(db->dev, "%s: Invalid ethernet MAC address. Please "
# "set using ifconfig/n", ndev->name);
# #endif
#
# platform_set_drvdata(pdev, ndev);
# ret = register_netdev(ndev);
#
# if (ret == 0)
# printk(KERN_INFO "%s: dm9000%c at %p,%p IRQ %d MAC: %pM (%s)/n",
# ndev->name, dm9000_type_to_char(db->type),
# db->io_addr, db->io_data, ndev->irq,
# ndev->dev_addr, mac_src);
# return 0;
#
# out:
# #if defined(CONFIG_ARCH_S3C2410)
# *(volatile unsigned int *)S3C2410_BWSCON = oldval_bwscon;
# *(volatile unsigned int *)S3C2410_BANKCON4 = oldval_bankcon4;
# #endif
# dev_err(db->dev, "not found (%d)./n", ret);
#
# dm9000_release_board(pdev, db);
# free_netdev(ndev);
#
# return ret;
# }
a.第24-27行定义了两个变量，用来保存BWSCON和BANKCON4的值，下面将会用到。
b.第32-39对BANK4进行了设置。首先设置BWSCON，
9对BANK4进行了设置。首先设置BWSCON，
#if defined(CONFIG_ARCH_S3C2410)
*((volatile unsigned int *)S3C2410_BWSCON) =
(oldval_bwscon & ~(3<<16)) | S3C2410_BWSCON_DW4_16 | S3C2410_BWSCON_WS4 | S3C2410_BWSCON_ST4;
*((volatile unsigned int *)S3C2410_BANKCON4) = 0x1f7c;
#endif
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#if defined(CONFIG_ARCH_S3C2410)
*((volatile unsigned int *)S3C2410_BWSCON) =
(oldval_bwscon & ~(3<<16)) | S3C2410_BWSCON_DW4_16 | S3C2410_BWSCON_WS4 | S3C2410_BWSCON_ST4;
*((volatile unsigned int *)S3C2410_BANKCON4) = 0x1f7c;
#endif
#if defined(CONFIG_ARCH_S3C2410)
*((volatile unsigned int *)S3C2410_BWSCON) =
(oldval_bwscon & ~(3<<16)) | S3C2410_BWSCON_DW4_16 | S3C2410_BWSCON_WS4 | S3C2410_BWSCON_ST4;
*((volatile unsigned int *)S3C2410_BANKCON4) = 0x1f7c;
#endif
主要是设置了总线宽度16，nWAIT，ST。（具体的可以参考s3c2440数据手册的BUS WIDTH & WAIT CONTROL REGISTER (BWSCON)）。然后设置BANKCON4的时间参数，值为0×1f7c（pmc:normal Tacp:6clk Tcah:4clk Tcoh:1clk Tacc:14clk Tcos:4clk 具体可以参考s3c2440数据手册的BANK CONTROL REGISTER）
c.第209-216的代码是我自己给注释的，据其意思，上面首先给MAC赋值，然后检测合法性，但经实践，判断语句总成立，所以在linux启动注册dm9000时总输出Invalid ethernet MAC address.反正后面也会再次给MAC地址赋值，所以干脆把这几行代码注释掉。
d.第218-227行就是给MAC地址赋值的，听说赋什么值都可以，有这么神奇吗？
e.第266-269行恢复寄存器原来的值。
f.以上的步骤和代码都是参考书上的，但可惜的是，按照上面步骤去修改，系统能成功加载dm9000驱动，但无法ping通，这个事确实让我很苦恼，上网找了很多资料，最后发现大多数都需要调用writel来设置BWSCON、GPFCON和中断等。所以无计之下参考了mini2440中的一段代码，出自附送光盘的无操作系统代码测试的dm9000部分。
到此 ，代码的移植到此为止，然后是配置内核，以使用dm9000。在
-> Device Drivers
--> Network device support
--> Network device support (NETDEVICES [=y])
--> Ethernet (10 or 100Mbit) 处将DM9000网卡选为编译进内核。
然后在/etc/init.d/rcS文件的开始处加入
ifconfig
eth0 192.168.1.22<
pre>
当然，ip地址是因人而定的，尽量设为和PC在同一个网段。重新将内核下载到开发板后启动