Linux 块设备驱动代码编写
<p>按照ldd的说法，linux的设备驱动包括了char，block，net三种设备。char设备是比较简单的，只要分配了major、minor号，就可以进行读写处理了。相对而言，block和net要稍微复杂些。net设备姑且按下不谈，我们在以后的博文中会有涉及。今天，我们可以看看一个简单的block是怎么设计的。</p>
<p>
为了将block和fs分开，kernel的设计者定义了request queue这一种形式。换一句话说，所有fs对block设备的请求，最终都会转变为request的形式。所以，对于block设备驱动开发的朋友来说，处理好了request queue就掌握了block设备的一半。当然，block设备很多，hd、floppy、ram都可以这么来定义，有兴趣的朋友可以在drivers/block寻找相关的代码来阅读。兴趣没有那么强的同学，可以看看我们这篇博文，基本上也能学个大概。有个基本的概念，再加上一个简单浅显的范例，对于一般的朋友来说，已经足够了。</p>
<p>
闲话不多说，我们看看一个ramdisk代码驱动是怎么写的，代码来自《深入linux 设备驱动程序内核机制》，</p>
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<code class="cpp preprocessor">#include <linux/module.h> </code>
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<code class="cpp preprocessor">#include <linux/kernel.h> </code>
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<code class="cpp preprocessor">#include <linux/init.h> </code>
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<code class="cpp spaces"> </code>
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<code class="cpp preprocessor">#include <linux/fs.h> </code>
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<code class="cpp preprocessor">#include <linux/types.h> </code>
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<code class="cpp preprocessor">#include <linux/fcntl.h> </code>
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<code class="cpp preprocessor">#include <linux/vmalloc.h> </code>
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<code class="cpp preprocessor">#include <linux/blkdev.h> </code>
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<code class="cpp preprocessor">#include <linux/hdreg.h> </code>
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<code class="cpp spaces"> </code>
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<code class="cpp preprocessor">#define RAMHD_NAME "ramhd" </code>
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<code class="cpp preprocessor">#define RAMHD_MAX_DEVICE 2 </code>
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<div class="line number14 index13 alt1">
<code class="cpp preprocessor">#define RAMHD_MAX_PARTITIONS 4 </code>
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<code class="cpp spaces"> </code>
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<code class="cpp preprocessor">#define RAMHD_SECTOR_SIZE 512 </code>
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<code class="cpp preprocessor">#define RAMHD_SECTORS 16 </code>
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<code class="cpp preprocessor">#define RAMHD_HEADS 4 </code>
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<code class="cpp preprocessor">#define RAMHD_CYLINDERS 256 </code>
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<code class="cpp spaces"> </code>
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<code class="cpp preprocessor">#define RAMHD_SECTOR_TOTAL (RAMHD_SECTORS * RAMHD_HEADS *RAMHD_CYLINDERS) </code>
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<code class="cpp preprocessor">#define RAMHD_SIZE (RAMHD_SECTOR_SIZE * RAMHD_SECTOR_TOTAL) //8mb </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">typedef</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">{ </code>
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<code class="cpp spaces"> </code><code class="cpp plain">unsigned </code><code class="cpp color1 bold">char</code><code class="cpp plain">* data; </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">request_queue* queue; </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">gendisk* gd; </code>
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<code class="cpp plain">}RAMHD_DEV; </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">char</code><code class="cpp plain">* sdisk = {NULL}; </code>
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<code class="cpp keyword bold">static</code> <code class="cpp plain">RAMHD_DEV* rdev = {NULL}; </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">static</code> <code class="cpp plain">dev_t ramhd_major; </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">ramhd_space_init(</code><code class="cpp keyword bold">void</code><code class="cpp plain">) </code>
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<code class="cpp plain">{ </code>
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<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
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<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">err = 0; </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i = 0; i < RAMHD_MAX_DEVICE; i++){ </code>
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<code class="cpp spaces"> </code><code class="cpp plain">sdisk = vmalloc(RAMHD_SIZE); </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(!sdisk){ </code>
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<code class="cpp spaces"> </code><code class="cpp plain">err = -ENOMEM; </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">err; </code>
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<code class="cpp spaces"> </code><code class="cpp plain">} </code>
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<code class="cpp spaces"> </code>
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<code class="cpp spaces"> </code><code class="cpp functions bold">memset</code><code class="cpp plain">(sdisk, 0, RAMHD_SIZE); </code>
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<code class="cpp spaces"> </code><code class="cpp plain">} </code>
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<div class="line number48 index47 alt1">
<code class="cpp spaces"> </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">err; </code>
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<code class="cpp plain">} </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">void</code> <code class="cpp plain">ramhd_space_clean(</code><code class="cpp keyword bold">void</code><code class="cpp plain">) </code>
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<code class="cpp plain">{ </code>
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<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i = 0; i < RAMHD_MAX_DEVICE; i++){ </code>
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<code class="cpp spaces"> </code><code class="cpp plain">vfree(sdisk); </code>
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<code class="cpp spaces"> </code><code class="cpp plain">} </code>
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<code class="cpp plain">} </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">ramhd_open(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">block_device* bdev, fmode_t mode) </code>
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<code class="cpp plain">{ </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
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<code class="cpp plain">} </code>
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<code class="cpp spaces"> </code>
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<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">ramhd_release(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">gendisk*gd, fmode_t mode) </code>
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<code class="cpp plain">{ </code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
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<code class="cpp plain">} </code>
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<code class="cpp spaces"> </code>
</div>
<div class="line number70 index69 alt1">
<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">ramhd_ioctl(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">block_device* bdev, fmode_t mode, unsigned </code><code class="cpp color1 bold">int</code> <code class="cpp plain">cmd, unsigned </code><code class="cpp color1 bold">long</code> <code class="cpp plain">arg) </code>
</div>
<div class="line number71 index70 alt2">
<code class="cpp plain">{ </code>
</div>
<div class="line number72 index71 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">err; </code>
</div>
<div class="line number73 index72 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">hd_geometry geo; </code>
</div>
<div class="line number74 index73 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number75 index74 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">switch</code><code class="cpp plain">(cmd) </code>
</div>
<div class="line number76 index75 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number77 index76 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">case</code> <code class="cpp plain">HDIO_GETGEO: </code>
</div>
<div class="line number78 index77 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">err = !access_ok(VERIFY_WRITE, arg, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(geo)); </code>
</div>
<div class="line number79 index78 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(err) </code>
</div>
<div class="line number80 index79 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-EFAULT; </code>
</div>
<div class="line number81 index80 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number82 index81 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">geo.cylinders = RAMHD_CYLINDERS; </code>
</div>
<div class="line number83 index82 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">geo.heads = RAMHD_HEADS; </code>
</div>
<div class="line number84 index83 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">geo.sectors = RAMHD_SECTORS; </code>
</div>
<div class="line number85 index84 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">geo.start = get_start_sect(bdev); </code>
</div>
<div class="line number86 index85 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number87 index86 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(copy_to_user((</code><code class="cpp keyword bold">void</code><code class="cpp plain">*)arg, &geo, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(geo))) </code>
</div>
<div class="line number88 index87 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-EFAULT; </code>
</div>
<div class="line number89 index88 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number90 index89 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
</div>
<div class="line number91 index90 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number92 index91 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number93 index92 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-ENOTTY; </code>
</div>
<div class="line number94 index93 alt1">
<code class="cpp plain">} </code>
</div>
<div class="line number95 index94 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number96 index95 alt1">
<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">block_device_operations ramhd_fops = { </code>
</div>
<div class="line number97 index96 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.owner = THIS_MODULE, </code>
</div>
<div class="line number98 index97 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.open = ramhd_open, </code>
</div>
<div class="line number99 index98 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.release = ramhd_release, </code>
</div>
<div class="line number100 index99 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.ioctl = ramhd_ioctl, </code>
</div>
<div class="line number101 index100 alt2">
<code class="cpp plain">}; </code>
</div>
<div class="line number102 index101 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number103 index102 alt2">
<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">ramhd_make_request(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">request_queue* q, </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">bio* bio) </code>
</div>
<div class="line number104 index103 alt1">
<code class="cpp plain">{ </code>
</div>
<div class="line number105 index104 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code><code class="cpp plain">* pRHdata; </code>
</div>
<div class="line number106 index105 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code><code class="cpp plain">* pBuffer; </code>
</div>
<div class="line number107 index106 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">bio_vec* bvec; </code>
</div>
<div class="line number108 index107 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
</div>
<div class="line number109 index108 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">err = 0; </code>
</div>
<div class="line number110 index109 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number111 index110 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">block_device* bdev = bio->bi_bdev; </code>
</div>
<div class="line number112 index111 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">RAMHD_DEV* pdev = bdev->bd_disk->private_data; </code>
</div>
<div class="line number113 index112 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number114 index113 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(((bio->bi_sector * RAMHD_SECTOR_SIZE) + bio->bi_size) > RAMHD_SIZE){ </code>
</div>
<div class="line number115 index114 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">err = -EIO; </code>
</div>
<div class="line number116 index115 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">err; </code>
</div>
<div class="line number117 index116 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number118 index117 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number119 index118 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">pRHdata = pdev->data + (bio->bi_sector * RAMHD_SECTOR_SIZE); </code>
</div>
<div class="line number120 index119 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">bio_for_each_segment(bvec, bio, i){ </code>
</div>
<div class="line number121 index120 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">pBuffer = kmap(bvec->bv_page) + bvec->bv_offset; </code>
</div>
<div class="line number122 index121 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">switch</code><code class="cpp plain">(bio_data_dir(bio)){ </code>
</div>
<div class="line number123 index122 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">case</code> <code class="cpp plain">READ: </code>
</div>
<div class="line number124 index123 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">memcpy</code><code class="cpp plain">(pBuffer, pRHdata, bvec->bv_len); </code>
</div>
<div class="line number125 index124 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">flush_dcache_page(bvec->bv_page); </code>
</div>
<div class="line number126 index125 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number127 index126 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number128 index127 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">case</code> <code class="cpp plain">WRITE: </code>
</div>
<div class="line number129 index128 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">flush_dcache_page(bvec->bv_page); </code>
</div>
<div class="line number130 index129 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">memcpy</code><code class="cpp plain">(pRHdata, pBuffer, bvec->bv_len); </code>
</div>
<div class="line number131 index130 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number132 index131 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number133 index132 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">default</code><code class="cpp plain">: </code>
</div>
<div class="line number134 index133 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">kunmap(bvec->bv_page); </code>
</div>
<div class="line number135 index134 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">goto</code> <code class="cpp plain">out; </code>
</div>
<div class="line number136 index135 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number137 index136 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number138 index137 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">kunmap(bvec->bv_page); </code>
</div>
<div class="line number139 index138 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">pRHdata += bvec->bv_len; </code>
</div>
<div class="line number140 index139 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number141 index140 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number142 index141 alt1">
<code class="cpp plain">out: </code>
</div>
<div class="line number143 index142 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">bio_endio(bio, err); </code>
</div>
<div class="line number144 index143 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
</div>
<div class="line number145 index144 alt2">
<code class="cpp plain">} </code>
</div>
<div class="line number146 index145 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number147 index146 alt2">
<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">alloc_ramdev(</code><code class="cpp keyword bold">void</code><code class="cpp plain">) </code>
</div>
<div class="line number148 index147 alt1">
<code class="cpp plain">{ </code>
</div>
<div class="line number149 index148 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
</div>
<div class="line number150 index149 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i = 0; i < RAMHD_MAX_DEVICE; i++){ </code>
</div>
<div class="line number151 index150 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rdev = kzalloc(</code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(RAMHD_DEV), GFP_KERNEL); </code>
</div>
<div class="line number152 index151 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(!rdev){ </code>
</div>
<div class="line number153 index152 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-ENOMEM; </code>
</div>
<div class="line number154 index153 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number155 index154 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number156 index155 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number157 index156 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
</div>
<div class="line number158 index157 alt1">
<code class="cpp plain">} </code>
</div>
<div class="line number159 index158 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number160 index159 alt1">
<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">void</code> <code class="cpp plain">clean_ramdev(</code><code class="cpp keyword bold">void</code><code class="cpp plain">) </code>
</div>
<div class="line number161 index160 alt2">
<code class="cpp plain">{ </code>
</div>
<div class="line number162 index161 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
</div>
<div class="line number163 index162 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number164 index163 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i = 0; i < RAMHD_MAX_DEVICE; i++){ </code>
</div>
<div class="line number165 index164 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(rdev) </code>
</div>
<div class="line number166 index165 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">kfree(rdev); </code>
</div>
<div class="line number167 index166 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number168 index167 alt1">
<code class="cpp plain">} </code>
</div>
<div class="line number169 index168 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number170 index169 alt1">
<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code> <code class="cpp plain">__init ramhd_init(</code><code class="cpp keyword bold">void</code><code class="cpp plain">) </code>
</div>
<div class="line number171 index170 alt2">
<code class="cpp plain">{ </code>
</div>
<div class="line number172 index171 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
</div>
<div class="line number173 index172 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number174 index173 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">ramhd_space_init(); </code>
</div>
<div class="line number175 index174 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">alloc_ramdev(); </code>
</div>
<div class="line number176 index175 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number177 index176 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ramhd_major = register_blkdev(0, RAMHD_NAME); </code>
</div>
<div class="line number178 index177 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number179 index178 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i = 0; i < RAMHD_MAX_DEVICE; i++){ </code>
</div>
<div class="line number180 index179 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->data = sdisk; </code>
</div>
<div class="line number181 index180 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->queue = blk_alloc_queue(GFP_KERNEL); </code>
</div>
<div class="line number182 index181 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">blk_queue_make_request(rdev->queue, ramhd_make_request); </code>
</div>
<div class="line number183 index182 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number184 index183 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd = alloc_disk(RAMHD_MAX_PARTITIONS); </code>
</div>
<div class="line number185 index184 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd->major = ramhd_major; </code>
</div>
<div class="line number186 index185 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd->first_minor = i * RAMHD_MAX_PARTITIONS; </code>
</div>
<div class="line number187 index186 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd->fops = &ramhd_fops; </code>
</div>
<div class="line number188 index187 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd->queue = rdev->queue; </code>
</div>
<div class="line number189 index188 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd->private_data = rdev; </code>
</div>
<div class="line number190 index189 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">sprintf</code><code class="cpp plain">(rdev->gd->disk_name, </code><code class="cpp string">"ramhd%c"</code><code class="cpp plain">, </code><code class="cpp string">'a'</code> <code class="cpp plain">+i); </code>
</div>
<div class="line number191 index190 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rdev->gd->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; </code>
</div>
<div class="line number192 index191 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">set_capacity(rdev->gd, RAMHD_SECTOR_TOTAL); </code>
</div>
<div class="line number193 index192 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">add_disk(rdev->gd); </code>
</div>
<div class="line number194 index193 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number195 index194 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number196 index195 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
</div>
<div class="line number197 index196 alt2">
<code class="cpp plain">} </code>
</div>
<div class="line number198 index197 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number199 index198 alt2">
<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">void</code> <code class="cpp plain">__exit ramhd_exit(</code><code class="cpp keyword bold">void</code><code class="cpp plain">) </code>
</div>
<div class="line number200 index199 alt1">
<code class="cpp plain">{ </code>
</div>
<div class="line number201 index200 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i; </code>
</div>
<div class="line number202 index201 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i = 0; i < RAMHD_MAX_DEVICE; i++){ </code>
</div>
<div class="line number203 index202 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">del_gendisk(rdev->gd); </code>
</div>
<div class="line number204 index203 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">put_disk(rdev->gd); </code>
</div>
<div class="line number205 index204 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">blk_cleanup_queue(rdev->queue); </code>
</div>
<div class="line number206 index205 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number207 index206 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number208 index207 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">clean_ramdev(); </code>
</div>
<div class="line number209 index208 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ramhd_space_clean(); </code>
</div>
<div class="line number210 index209 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">unregister_blkdev(ramhd_major, RAMHD_NAME); </code>
</div>
<div class="line number211 index210 alt2">
<code class="cpp plain">} </code>
</div>
<div class="line number212 index211 alt1">
<code class="cpp spaces"> </code>
</div>
<div class="line number213 index212 alt2">
<code class="cpp plain">module_init(ramhd_init); </code>
</div>
<div class="line number214 index213 alt1">
<code class="cpp plain">module_exit(ramhd_exit); </code>
</div>
<div class="line number215 index214 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number216 index215 alt1">
<code class="cpp plain">MODULE_AUTHOR(</code><code class="cpp string">"dennis__chen@ AMDLinuxFGL"</code><code class="cpp plain">); </code>
</div>
<div class="line number217 index216 alt2">
<code class="cpp plain">MODULE_DESCRIPTION(</code><code class="cpp string">"The ramdisk implementation with request function"</code><code class="cpp plain">); </code>
</div>
<div class="line number218 index217 alt1">
<code class="cpp plain">MODULE_LICENSE(</code><code class="cpp string">"GPL"</code><code class="cpp plain">);</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
为了大家方便，顺便也把Makefile放出来，看过前面blog的朋友都知道，这其实很简单，</p>
<div class="jb51code">
<div>
<div class="syntaxhighlightercpp" id="highlighter_314294">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
<div class="line number9 index8 alt2">
9</div>
<div class="line number10 index9 alt1">
10</div>
<div class="line number11 index10 alt2">
11</div>
<div class="line number12 index11 alt1">
12</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="cpp plain">ifneq ($(KERNELRELEASE),) </code>
</div>
<div class="line number2 index1 alt1">
<code class="cpp plain">obj-m := ramdisk.o </code>
</div>
<div class="line number3 index2 alt2">
<code class="cpp spaces"> </code>
</div>
<div class="line number4 index3 alt1">
<code class="cpp keyword bold">else</code>
</div>
<div class="line number5 index4 alt2">
<code class="cpp plain">PWD := $(shell pwd) </code>
</div>
<div class="line number6 index5 alt1">
<code class="cpp plain">KVER := $(shell uname -r) </code>
</div>
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<code class="cpp plain">KDIR := /lib/modules/$(KVER)/build </code>
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<div class="line number8 index7 alt1">
<code class="cpp plain">all: </code>
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<div class="line number9 index8 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">$(MAKE) -C $(KDIR) M=$(PWD) modules </code>
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<div class="line number10 index9 alt1">
<code class="cpp plain">clean: </code>
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<div class="line number11 index10 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versions modules.* Module.* </code>
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<div class="line number12 index11 alt1">
<code class="cpp plain">endif </code>
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<p>
这段代码究竟有没有用呢？可以按照下面的步骤来做，</p>
<p>
a）make 一下，生成ramdisk.ko；</p>
<p>
b）编译好了之后，就可以安装驱动了，在linux下是这么做的，sudo insmod ramdisk.ko；</p>
<p>
c）安装好了，利用ls /dev/ramhd*， 就会发现在/dev下新增两个结点，即/dev/ramhda和/dev/ramhdb；</p>
<p>
d）不妨选择其中一个节点进行分区处理， sudo fdisk /dev/ramhda，简单处理的话就建立一个分区， 生成/dev/ramhda1；</p>
<p>
e）创建文件系统，sudo mkfs.ext3 /dev/ramhda1；</p>
<p>
f）有了上面的文件系统，就可以进行mount处理，不妨sudo mount /dev/ramhda1 /mnt；</p>
<p>
g）上面都弄好了，大家就可以copy、delete文件试试了，是不是很简单。</p>
<p>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。</p>
<p>
原文链接：https://blog.csdn.net/feixiaoxing/article/details/11701797</p>
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