proc的妙用

今天在在公司做网络驱动开发测试时，随机包出现收包计数停止的现象，当时怀疑是DMA rx buffer不足导致，想通过对比收发包正常和收发包不正常是DMA相关寄存器的情况。

后跟踪代码，若在收发包里面增加打印，必定回降低收发包性能，对比结果也就不准了，分析代码分析来分析去，最终发现做合适的就是采用proc。

 /*
  * procfs_example.c: an example proc interface
  *
  * Copyright (C) 2001, Erik Mouw (mouw@nl.linux.org)
  *
  * This file accompanies the procfs-guide in the Linux kernel
  * source. Its main use is to demonstrate the concepts and
  * functions described in the guide.
  *
  * This software has been developed while working on the LART
  * computing board (http://www.lartmaker.nl), which was sponsored
  * by the Delt University of Technology projects Mobile Multi-media
  * Communications and Ubiquitous Communications.
  *
  * This program is free software; you can redistribute
  * it and/or modify it under the terms of the GNU General
  * Public License as published by the Free Software
  * Foundation; either version 2 of the License, or (at your
  * option) any later version.
  *
  * This program is distributed in the hope that it will be
  * useful, but WITHOUT ANY WARRANTY; without even the implied
  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  * PURPOSE.  See the GNU General Public License for more
  * details.
  *
  * You should have received a copy of the GNU General Public
  * License along with this program; if not, write to the
  * Free Software Foundation, Inc., 59 Temple Place,
  * Suite 330, Boston, MA  02111-1307  USA
  *
  */  

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/proc_fs.h>
 #include <linux/jiffies.h>
 #include <asm/uaccess.h>  

 #define MODULE_VERS "1.0"
 #define MODULE_NAME "procfs_example"  

 #define FOOBAR_LEN 8  

 struct fb_data_t {
     char name[FOOBAR_LEN + ];
     char value[FOOBAR_LEN + ];
 };  

 static struct proc_dir_entry *example_dir, *foo_file,
     *bar_file, *jiffies_file, *symlink;  

 struct fb_data_t foo_data, bar_data;  

 static int proc_read_jiffies(char *page, char **start,
                  off_t off, int count,
                  int *eof, void *data)
 {
     int len;  

     len = sprintf(page, "jiffies = %ld\n",
                       jiffies);  

     return len;
 }  

 static int proc_read_foobar(char *page, char **start,
                 off_t off, int count,
                 int *eof, void *data)
 {
     int len;
     struct fb_data_t *fb_data = (struct fb_data_t *)data;  

     /* DON'T DO THAT - buffer overruns are bad */
     len = sprintf(page, "%s = '%s'\n",
               fb_data->name, fb_data->value);  

     return len;
 }  

 static int proc_write_foobar(struct file *file,
                  const char *buffer,
                  unsigned long count,
                  void *data)
 {
     int len;
     struct fb_data_t *fb_data = (struct fb_data_t *)data;  

     if(count > FOOBAR_LEN)
         len = FOOBAR_LEN;
     else
         len = count;  

     if(copy_from_user(fb_data->value, buffer, len))
         return -EFAULT;  

     fb_data->value[len] = '\0';  

     return len;
 }  

 static int __init init_procfs_example(void)
 {
     int rv = ;  

     /* create directory */
     example_dir = proc_mkdir(MODULE_NAME, NULL);
     if(example_dir == NULL) {
         rv = -ENOMEM;
         goto out;
     }
     /* create jiffies using convenience function */
     jiffies_file = create_proc_read_entry("jiffies",
                           , example_dir,
                           proc_read_jiffies,
                           NULL);
     if(jiffies_file == NULL) {
         rv  = -ENOMEM;
         goto no_jiffies;
     }  

     /* create foo and bar files using same callback
      * functions
      */
     foo_file = create_proc_entry("foo", , example_dir);
     if(foo_file == NULL) {
         rv = -ENOMEM;
         goto no_foo;
     }  

     strcpy(foo_data.name, "foo");
     strcpy(foo_data.value, "foo");
     foo_file->data = &foo_data;
     foo_file->read_proc = proc_read_foobar;
     foo_file->write_proc = proc_write_foobar;  

     bar_file = create_proc_entry("bar", , example_dir);
     if(bar_file == NULL) {
         rv = -ENOMEM;
         goto no_bar;
     }  

     strcpy(bar_data.name, "bar");
     strcpy(bar_data.value, "bar");
     bar_file->data = &bar_data;
     bar_file->read_proc = proc_read_foobar;
     bar_file->write_proc = proc_write_foobar;  

     /* create symlink */
     symlink = proc_symlink("jiffies_too", example_dir,
                    "jiffies");
     if(symlink == NULL) {
         rv = -ENOMEM;
         goto no_symlink;
     }  

     /* everything OK */
     printk(KERN_INFO "%s %s initialised\n",
            MODULE_NAME, MODULE_VERS);
     return ;  

 no_symlink:
     remove_proc_entry("bar", example_dir);
 no_bar:
     remove_proc_entry("foo", example_dir);
 no_foo:
     remove_proc_entry("jiffies", example_dir);
 no_jiffies:
     remove_proc_entry(MODULE_NAME, NULL);
 out:
     return rv;
 }  

 static void __exit cleanup_procfs_example(void)
 {
     remove_proc_entry("jiffies_too", example_dir);
     remove_proc_entry("bar", example_dir);
     remove_proc_entry("foo", example_dir);
     remove_proc_entry("jiffies", example_dir);
     remove_proc_entry(MODULE_NAME, NULL);  

     printk(KERN_INFO "%s %s removed\n",
            MODULE_NAME, MODULE_VERS);
 }  

 module_init(init_procfs_example);
 module_exit(cleanup_procfs_example);  

 MODULE_AUTHOR("Erik Mouw");
 MODULE_DESCRIPTION("procfs examples");
 MODULE_LICENSE("GPL");  

驱动编译脚本Makefile文件如下：

    obj-m += proc.o
        CURRENT_PATH:=$(shell pwd)
            LINUX_KERNEL_PATH:=/lib/modules/$(shell uname -r)/build
    all:
            $(MAKE) -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules
    clean:
           rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versions

本人是在ubuntu10.04下编译。