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POWrite timer in Linux device driver
 

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  1. POWrite timer in Linux device driver
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    <p>I'm newbies with the module linux. I try to create a counter module where the counter is increment on timer callback. The result of the counter must be send to an other module (a memory module).</p> <pre><code>#include &lt;linux/init.h&gt; #include &lt;linux/module.h&gt; #include &lt;linux/kernel.h&gt; #include &lt;linux/slab.h&gt; #include &lt;linux/fs.h&gt; #include &lt;linux/errno.h&gt; #include &lt;linux/types.h&gt; #include &lt;linux/proc_fs.h&gt; #include &lt;linux/fcntl.h&gt; #include &lt;asm/system.h&gt; #include &lt;asm/uaccess.h&gt; MODULE_AUTHOR("Helene"); MODULE_DESCRIPTION("Module memory"); MODULE_SUPPORTED_DEVICE("none"); MODULE_LICENSE("Dual BSD/GPL"); /* Global variables of the driver */ /* Buffer to store data */ char *memory_buffer; int result; struct file_operations memory_fops; int memory_open(struct inode *inode, struct file *filp) { // printk(KERN_DEBUG "Opening memory module\n"); return 0; } int memory_release(struct inode *inode, struct file *filp) { // printk(KERN_DEBUG "Releasing of memory module\n"); return 0; } ssize_t memory_read(struct file *filp, char *buf, size_t count, loff_t *f_pos){ // printk(KERN_DEBUG "Reading memory module : %s\n", buf); if (*f_pos &gt; 0) return 0; if (count &gt; strlen(memory_buffer)) count = strlen(memory_buffer); copy_to_user(buf,memory_buffer,count); *f_pos = *f_pos + count; return count; } ssize_t memory_write( struct file *filp, const char *buf, size_t count, loff_t *f_pos) { // printk(KERN_DEBUG "Writing memory module : %s\n", buf); copy_from_user(memory_buffer, buf, count); return count; } static int __init memory_init(void) { /* Registering device */ result = register_chrdev(0, "memory", &amp;memory_fops); if (result &lt; 0) { printk(KERN_DEBUG "memory: cannot obtain major number \n"); return result; } /* Allocating memory for the buffer */ memory_buffer = kmalloc(1, GFP_KERNEL); if (!memory_buffer) { result = -ENOMEM; goto fail; } memset(memory_buffer, 0, 1); printk(KERN_ALERT "Inserting memory module : %d\n", result); return 0; fail: //memory_exit(); return result; } static void __exit memory_exit(void) { /* Freeing the major number */ unregister_chrdev(result, "memory"); /* Freeing buffer memory */ if (memory_buffer) { kfree(memory_buffer); } printk(KERN_DEBUG "Removing memory module\n"); } struct file_operations memory_fops = { owner: THIS_MODULE, read: memory_read, write: memory_write, open: memory_open, release: memory_release }; module_init(memory_init); module_exit(memory_exit); </code></pre> <p>The memory module works. My problem is when I call the function : filp_open/fp->f_op->write/filp_close on the function timer callback. I have test these functions out of the timer callback and it's work.</p> <p>Why the filp_open function (&amp; co) don't work on timer callback function ?</p> <pre><code>#include &lt;linux/init.h&gt; #include &lt;linux/module.h&gt; #include &lt;linux/kernel.h&gt; /* printk() */ #include &lt;linux/slab.h&gt; /* kmalloc() */ #include &lt;linux/fs.h&gt; /* everything... */ #include &lt;linux/errno.h&gt; /* error codes */ #include &lt;linux/types.h&gt; /* size_t */ #include &lt;linux/proc_fs.h&gt; #include &lt;linux/fcntl.h&gt; /* O_ACCMODE */ #include &lt;asm/system.h&gt; /* cli(), *_flags */ #include &lt;asm/uaccess.h&gt; /* copy_from/to_user */ MODULE_LICENSE("GPL"); static struct timer_list my_timer; int cptNbClic ; int result; struct file_operations timer_fops; int write_file_system(struct file *fp, char * buf){ int nb; mm_segment_t old_fs=get_fs(); set_fs(get_ds()); nb = fp-&gt;f_op-&gt;write(fp,buf ,10, &amp;fp-&gt;f_pos); set_fs(old_fs); return nb; } void writeInMemory(void){ // printk(KERN_DEBUG "busy %d\n", busy); int nbwrite; char buf[3]; int fmemory; fmemory=filp_open ("/dev/memory", O_WRONLY | O_APPEND | O_CREAT,0); //don't work on this function if (fmemory==NULL){//verification de l'ouverture printk(KERN_ALERT "filp_open error input memory!!.\n"); return -1; } sprintf(buf, "%d", cptNbClic); printk(KERN_DEBUG "%d\n", cptNbClic); nbwrite = write_file_system(fmemory, buf); filp_close(fmemory, 0); } void my_timer_callback( unsigned long data ) { cptNbClic++; printk(KERN_DEBUG "cptNbClic %d\n", cptNbClic); writeInMemory(); setup_timer(&amp;my_timer, my_timer_callback, 0); mod_timer(&amp;my_timer, jiffies + msecs_to_jiffies(1000)); } static int timer_open(struct inode *inode, struct file *filp) { /* setup your timer to call my_timer_callback */ cptNbClic = 0; setup_timer(&amp;my_timer, my_timer_callback, 0); /* setup timer interval to 200 msecs */ mod_timer(&amp;my_timer, jiffies + msecs_to_jiffies(1000)); return 0; } static int timer_release(struct inode *inode, struct file *filp) { /* Success */ printk(KERN_DEBUG "Releasing of cpt module\n"); del_timer(&amp;my_timer); return 0; } static int __init timer_init(void) { /* Registering device */ result = register_chrdev(0, "timer", &amp;timer_fops); if (result &lt; 0) { printk(KERN_DEBUG "timer: cannot obtain major number \n"); return result; } printk(KERN_ALERT "Inserting timer module : %d\n", result); return 0; } static void __exit timer_exit(void) { unregister_chrdev(result, "timer"); printk(KERN_DEBUG "Removing timer module\n"); } struct file_operations timer_fops = { owner: THIS_MODULE, open: timer_open, release: timer_release }; /* Declaration of the init and exit functions */ module_init(timer_init); module_exit(timer_exit); </code></pre> <p>Sorry for my bad english</p>
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    1. PTQuestion
    1. USFurqan Safdar
    1. UShelene
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      1. VTUpMod
    1. COit there some specific reason that these modules **must** communicate though device files? generally, opening files form kernel space is not a good idea.
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      1. USRaber
    2. COIn fact, it is just an exercise to develop later drivers of different devices. I trying to understand the operation
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      1. POWrite timer in Linux device driver
      1. UShelene
 

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