Re: [linux-pm] [RFC/RFT][PATCH -mm 2/5] swsusp: userland interface (rev. 2)

Greg KH
2006-01-04T23:49:18Z

On Wed, Jan 04, 2006 at 11:51:58PM +0100, Rafael J. Wysocki wrote:
> +static struct snapshot_dev interface = {
> + .name = "snapshot",
> +};
> +
> +static ssize_t snapshot_show(struct subsystem * subsys, char *buf)
> +{
> + return sprintf(buf, "%d:%d\n", MAJOR(interface.devno),
> + MINOR(interface.devno));
> +}
> +
> +static struct subsys_attribute snapshot_attr = {
> + .attr = {
> + .name = __stringify(snapshot),
> + .mode = S_IRUGO,
> + },
> + .show = snapshot_show,
> +};
> +
> +static int __init snapshot_dev_init(void)
> +{
> + int error;
> +
> + error = alloc_chrdev_region(&interface.devno, 0, 1, interface.name);
> + if (error)
> + return error;
> + cdev_init(&interface.cdev, &snapshot_fops);
> + interface.cdev.ops = &snapshot_fops;
> + error = cdev_add(&interface.cdev, interface.devno, 1);
> + if (error)
> + goto Unregister;
> + error = sysfs_create_file(&power_subsys.kset.kobj, &snapshot_attr.attr);

Heh, that's a neat hack, register a sysfs file that contains the
major:minor (there is a function that will print that the correct way,
if you really want to do that), in sysfs. It's better to just register
a misc character device with the name "snapshot", and then udev will
create your userspace node with the proper major:minor all automatically
for you.

Unless you want to turn these into syscalls :)

thanks,

greg k-h