[COLUG] Re: Linux Kernel Modules

[Travis Sidelinger]

Another follow-up from last Wednesday.

I figured out why my example with sysfs tree entries did not compile.  
class_simple has been moved from the kernel at version >= 2.6.13

Below is what's needed to create a simple sysfs class entry.  With a 
class entry, udev will receive a hotplug event and automatically create 
the /dev/chardev device node file.
...
    // Create sysfs entry for udev
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,13))
    chardev_class = class_create(THIS_MODULE,module_name);
    if(IS_ERR(chardev_class))
    {
        printk(KERN_ALERT "%s: failed to create sysfs entry\n", 
module_name);
        return(result);
        }
    class_device_create(chardev_class, NULL, devnum, NULL, module_name);
#else
    chardev_class = class_simple_create(THIS_MODULE,module_name);
    if(IS_ERR(chardev_class))
    {
        printk(KERN_ALERT "%s: failed to create sysfs entry\n", 
module_name);
        return(result);
        }
    class_simple_device_add(chardev_class, devnum, NULL, module_name);
#endif
...
    // Remove sysfs entry
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,13))
    class_device_destroy(chardev_class,devnum);
    class_destroy(chardev_class);
#else
    class_simple_device_remove(devnum);
    class_simple_destroy(chardev_class);
#endif

Here is the full program:
    http://www.ilive4unix.net/doku.php/code/linux#character_device

> Thanks everyone for your attention tonight.  Hopefully I didn't put 
> too many people to sleep.
>
> Here are my wiki notes this lecture was based on:
>  http://www.ilive4unix.net/doku.php/notes/unix/linux/device-drivers
>
> The open doc presentation file is posted on the wiki.
>
> My examples are posted here:
>   http://www.ilive4unix.net/doku.php/code/linux
>
> Errata:
>  - My sysfs example failed because the class_simple interface has been 
> removed from new kernel versions.  I will try to get an example posted 
> once I get some working code.  This example does work under CentOS 
> (kernel 2.6.9)
>  - I update my wiki notes for coping data to and from kernel space.
>  - Added /etc/modprobe.conf info
>
> Travis Sidelinger
>