linux kernel 1.0 网络模块代码分析——ddi.h和ddi.c

/*
 * ddi.c    Implement the Device Driver Interface (DDI) routines.
 *        Currently, this is only used by the NET layer of LINUX,
 *        but it eventually might move to an upper directory of
 *        the system.
 *
 * Version:    @(#)ddi.c    1.0.5    04/22/93
 *
 * Author:    Fred N. van Kempen, <[e-mail]>
 */
/*1.0版本首次加入网络部分的代码，所以代码设计还不是很完善。ddi.c/h实现了设备驱动接口(DDI)，后面计划把这部分代码移到更高的层次，作为所有设备的接口，而不是仅用于linux的网络层*/
#include <asm/segment.h>
#include <asm/system.h>
#include <linux/types.h>
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/ddi.h>

/*开启调试开关。使用printk来打印输出。*/
#undef    DDI_DEBUG
#ifdef    DDI_DEBUG
#   define PRINTK(x)    printk x
#else
#   define PRINTK(x)    /**/
#endif

/*声明全局的DDI设备控制块数组*/
extern struct ddi_device    devices[];    /* device driver map    */
/*用于设备网络协议*/
extern struct ddi_proto        protocols[];    /* network protocols    */
/*struct ddi_device和struct ddi_proto在ddi.h中定义*/

/*
 * This function gets called with an ASCII string representing the
 * ID of some DDI driver. We loop through the DDI Devices table
 * and return the address of the control block that has a matching
 * "name" field. It is used by upper-level layers that want to
 * dynamically bind some UNIX-domain "/dev/XXXX" file name to a
 * DDI device driver. The "iflink(8)" program is an example of
 * this behaviour.
 */
/*这个函数主要用于上层动态绑定一些UNIX域到一个DDI设备驱动。传入参数是ASCII字符串，代表一些DDI驱动的ID。我们遍历DDI设备表并返回name字段匹配传入参数的控制块。iflink(8)程序是这个行为的一个例子。*/
struct ddi_device *
ddi_map(const char *id)
{
  register struct ddi_device *dev;

  PRINTK (("DDI: MAP: looking for \"%s\": ", id));
  dev = devices;
  while (dev->title != NULL) {
    if (strncmp(dev->name, id, DDI_MAXNAME) == 0) {
        PRINTK (("OK at 0x%X\n", dev));
        return(dev);
    }
    dev++;
  }
  PRINTK (("NOT FOUND\n"));
  return(NULL);
}


/*
 * This is the function that is called by a kernel routine during
 * system startup. Its purpose is to walk trough the "devices"
 * table (defined above), and to call all moduled defined in it.
 */
/*这个函数在内核启动的函数中调用。它的目标是遍历“devices”表(上面定义的)，然后调用在“devices”表(上面定义的protocols和devices两个数组)里面定义的初始化函数对每个协议和设备进行初始化*/
void
ddi_init(void)
{
  struct ddi_proto *pro;
  struct ddi_device *dev;

  PRINTK (("DDI: Starting up!\n"));

  /* First off, kick all configured protocols. */
  pro = protocols;
  while (pro->name != NULL) {
    (*pro->init)(pro);
    pro++;
  }

  /* Done. Now kick all configured device drivers. */
  dev = devices;
  while (dev->title != NULL) {
    (*dev->init)(dev);
    dev++;
  }

  /* We're all done... */
}

/*
 * ddi.h    Define the structure for linking in I/O drivers into the
 *        operating system kernel. This method is currently only
 *        used by NET layer drivers, but it will be expanded into
 *        a link methos for ALL kernel-resident device drivers.
 *
 * Version:    @(#)ddi.h    1.0.2    04/22/93
 *
 * Author:    Fred N. van Kempen, <[e-mail]>
 */
/*ddi.h 定义了链接I/O驱动到操作系统核心的数据结构。目前只有内核网络层驱动使用这个方法，但以后这个方法会扩展成所有驻留内核的设备驱动的链接方法。*/
#ifndef _LINUX_DDI_H
#define _LINUX_DDI_H


/* DDI control block flags. */
/*DDI控制块标志位*/
#define DDI_FREADY    0x10000000    /* device is initialized *//*设备被初始化*/
#define DDI_FPRESENT    0x20000000    /* device hardware is present *//*设备硬件已存在*/
#define DDI_FBLKDEV    0x00000001    /* device has a BLK spec. file *//*设备有一个BLK spec.文件*/
#define DDI_FCHRDEV    0x00000002    /* device has a CHR spec. file *//*设备有一个CHR spec.文件*//*这些BLK/CHR spec.文件是什么?*/

/* Various constants. */
#define DDI_MAXNAME    16        /* length of a DDI ID string    */


/* This structure is used to set up a DDI driver. */
struct ddconf {
  int        ioaddr;            /* main I/O (port) address    */
  int        ioaux;            /* auxiliary I/O (HD, AST)    */
  int        irq;            /* IRQ channel            */
  int        dma;            /* DMA channel to use        */
  unsigned long    memsize;        /* size of onboard memory    */
  unsigned long    memaddr;        /* base address of memory    */
};


/* The DDI device control block. */
struct ddi_device {
  char        *title;            /* title of the driver        */
  char        name[DDI_MAXNAME];    /* unit name of the I/O driver    */
  short int    unit;            /* unit number of this driver    */
  short int    nunits;            /* number of units in driver    */
  int        (*init)(struct ddi_device *);    /* initialization func        */
  int        (*handler)(int, ...);    /* command handler        */
  short    int    major;            /* driver major dev number    */
  short    int    minor;            /* driver minor dev number    */
  unsigned long    flags;            /* various flags        */
  struct ddconf config;            /* driver HW setup        */
};


/* This structure is used to set up networking protocols. */
struct ddi_proto {
  char        *name;            /* protocol name        */
  void        (*init)(struct ddi_proto *);    /* initialization func    */
};


/* This structure is used to link a STREAMS interface. */
struct iflink {
  char        id[DDI_MAXNAME];    /* DDI ID string        */
  char        stream[DDI_MAXNAME];    /* STREAMS interface name    */
  int        family;            /* address (protocol) family    */
  unsigned int    flags;            /* any flags needed (unused)    */
};


/* DDI control requests. */
#define DDIOCSDBG    0x9000        /* set DDI debug level        */
#define DDIOCGNAME    0x9001        /* get DDI ID name        */
#define DDIOCGCONF    0x9002        /* get DDI HW config        */
#define DDIOCSCONF    0x9003        /* set DDI HW config        */


/* DDI global functions. */
extern void            ddi_init(void);
extern struct ddi_device    *ddi_map(const char *id);


#endif    /* _LINUX_DDI_H */