/*
 * This file controls the Device Driver Interface.  It allows a driver to
 * register a set of file operations and a major number.  This number can later
 * be used to find the correct operations for a device file.
 */

#include <nucleus/driver.h>
#include <nucleus/object.h>
#include <nucleus/vfs.h>

/* Structure for a Driver object */
struct Driver {
	Object obj;
	unsigned short major;
	FileOps *ops;
};

/* Driver object type */
ObjectType driverType = {
	.name = "DRIVER",
	.size = sizeof(Driver),
};

static ObjectList *drivers;

/* Compare the major numbers of two Drivers */
static int
compare_driver(void *a, void *b)
{
	Driver *da = a, *db = b;
	return (da->major - db->major);
}

/* Register a driver */
unsigned short
register_driver(unsigned short major, FileOps *ops)
{
	if (!drivers)
		drivers = create_list(&driverType, LIST_ORDERED,
		                      compare_driver);
	Driver *driver = new(&driverType);
	driver->major = major;
	driver->ops = ops;

	/* Ensure major is unique */
	if (!driver->major)
		driver->major = 1;
	Driver *collision;
	foreach (drivers, collision) {
		if (driver->major == collision->major)
			driver->major++;
		else if (driver->major < collision->major)
			break;
	}

	add(drivers, driver);
	return driver->major;
}

/* Find a driver from a major number */
FileOps *
find_driver(unsigned short major)
{
	Driver *driver;
	foreach (drivers, driver) {
		if (driver->major == major)
			break;
	}
	return driver->ops;
}