Re: driver model, duplicate names question

[Srinivas Pandruvada]

Thanks for the quick response. Here I am creating virtual devices using 
device_register.
I have attached a simple test program, which will give error.

This is my intention:

$> cd /sys/class/test_class
$> ls
power_zone_cpu_package_0
power_zone_cpu_package_1


$> cd power_zone_cpu_package_0
$> ls
power-zone-cpu-0

$> cd ..

$> cd power_zone_cpu_package_1
$> ls
power-zone-cpu-0


The error will be "
Error:
sysfs: cannot create duplicate filename '/class/test_class/power-zone-cpu-0'

I want to avoid a flat model, if there is a server system with many CPU 
packages with multiple cores in each.

Thanks,
Srinivas











On 07/16/2013 09:44 AM, Greg KH wrote:
> On Tue, Jul 16, 2013 at 09:34:57AM -0700, Srinivas Pandruvada wrote:
> > Hi Greg,
> >
> > I would like to create tree like structure using device model (struct
> > device, device_register/device_unregister) using parent/child
> > relationship while creation. I want to be able to create duplicate
> > names, when their parents are different, similar to a directory structure.
> > I see that I can't create devices with duplicate names (device names),
> > even when their parents are different.
> We actually check that?  Nice, I didn't realize that :)
>
> > How can I allow duplicate names when their parents are different devices?
> > I want to avoid flat model as I have parent child relationship and there
> > will be too many devices using flat model.
> Devices on the same bus shouldn't have the same name, but if they are in
> a "tree", it should be ok.  What check is erroring out?
>
> > Why, I need?
> > I am going to publish RFC for a new power cap class driver. We have a
> > multiple controllers under power cap class (they are devices). Under
> > which there are multiple power zones, with parent/child relationships.
> > Currently I have to use  kobject_init_and_add, which I want to avoid and
> > just use device_register. Other places, wherever such relationships are
> > required, kobjects are used like cpufreq.
> Yes, you shouldn't use "raw" kobject calls at all, so we should fix
> this.
>
> thanks,
>
> greg k-h

#include <linux/module.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/slab.h>

static struct device dev_par_0;
static struct device dev_par_0_child_0;

static struct device dev_par_1;
static struct device dev_par_1_child_0;


static struct class test_class_class = {
	.name = "test_class",
};

static int create_test_devices(void)
{
	int result;

	dev_set_name(&dev_par_0, "power_zone_cpu_package_0");

	dev_par_0.class = &test_class_class;
	result = device_register(&dev_par_0);
	if (result) {
		pr_err("device_register failed for parent_0\n");
		return result;
	}
	
	dev_set_name(&dev_par_1, "power_zone_cpu_package_1");
	dev_par_1.class = &test_class_class;
	result = device_register(&dev_par_1);
	if (result) {
		pr_err("device_register failed for parent_0\n");		
		goto error_par1;
	}
	

	dev_set_name(&dev_par_0_child_0, "power-zone-cpu-0");
	dev_par_0_child_0.class = &test_class_class;
	dev_par_0_child_0.parent = &dev_par_0;
	result = device_register(&dev_par_0_child_0);
	if (result) {
		pr_err("device_register failed for dev_par_0_child_0\n");		
		goto error_par0_child_0;
	}

	dev_set_name(&dev_par_1_child_0, "power-zone-cpu-0");
	dev_par_1_child_0.class = &test_class_class;
	dev_par_1_child_0.parent = &dev_par_1;
	result = device_register(&dev_par_1_child_0);
	if (result) {
		pr_err("device_register failed for dev_par_1_child_0\n");		
		goto error_par0_child_1;
	}

	return 0;

error_par0_child_1:
	device_unregister(&dev_par_0_child_0);
error_par0_child_0:
	device_unregister(&dev_par_1);
error_par1:
	device_unregister(&dev_par_0);

	return result;
}




static int __init dev_create_test_init(void)
{
	int result = 0;

	pr_debug("dev_create_test_init\n");
	result = class_register(&test_class_class);
	if (result)
		return result;

	result = create_test_devices();

	return result;
}

static void dev_create_test_exit(void)
{
	pr_debug("dev_create_test_exit\n");

	device_unregister(&dev_par_0_child_0);
	device_unregister(&dev_par_1_child_0);	
	device_unregister(&dev_par_0);
	device_unregister(&dev_par_1);

	class_unregister(&test_class_class);
}


module_init(dev_create_test_init)
module_exit(dev_create_test_exit)
MODULE_LICENSE("GPL v2");