Re: How to generate hotplug events in drivers?

[Stephen Glow <sglow@embeddedintelligence.com>]

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Greg KH wrote:
| udev needs to see a file called "dev" in the proper structure show up in
| the sysfs tree in either /sys/class/* or /sys/block/*.  So, you need to
| either use the misc char device interface, the block interface, some
| other char interface that already has sysfs support, or add your own.
| If you need to add your own, I suggest looking into the class_simple
| interface, as that's a lot easier to work with to start out with.
|
| Hope this helps,
|
| greg k-h

Hi Greg;

Thanks for the response, things seem to be working now.

I'm still a little fuzzy about how all this works together, but the
picture is starting to become a bit clearer.  Here are the basic steps I
took in my PCI driver to get the device node to show up, please let me
know if anyone sees an error here:

In the init module function, I create a new class_simple pointer:

static struct class_simple *myclass;

int init_module( void )
{
~    ...
~    myclass = class_simple_create( THIS_MODULE, "myclassname" );
~    ...
}

This causes the new class directory to show up under /sys/class

In the PCI probe function I do the following:

probe(...)
{
~   ...

~   // Allocate a device numer
~   dev_t mydev;
~   alloc_chrdev_region( &mydev, 0, 1, "mydevicename" );

~   // Add this device number to my class.  Note I'm passing NULL for
~   // the device pointer.  I'm not exactly sure what this is for, but
~   // most devices in the kernel tree seem to pass NULL here.
~   class_simple_add_device( myclass, mydev, NULL, "mydevicename" );

~   // Finally, I init and add my cdev structure.
~   cdev_init( &mycdev, &myfops );
~   mycdev.owner = THIS_MODULE;
~   kobject_set_name( &mycdev.kobj, "mydevicename" );
~   cdev_add( &mycdev, mydev, 1 );

~   ...
}

Of course, my real code has error checking and does cleanup in the PCI
remove function and the module exit function.

Thanks again!

Steve
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