ide: add warm-plug support for IDE devices (take 2)

* Add 'struct class ide_port_class' ('ide_port' class) and a 'struct
  device *portdev' ('ide_port' class device) in ide_hwif_t.

* Register 'ide_port' class in ide_init() and unregister it in
  cleanup_module().

* Create ->portdev in ide_register_port () and unregister it in
  ide_unregister().

* Add "delete_devices" class device attribute for unregistering IDE devices
  on a port and "scan" one for probing+registering IDE devices on a port.

* Add ide_sysfs_register_port() helper for registering "delete_devices"
  and "scan" attributes with ->portdev.  Call it in ide_device_add_all().

* Document IDE warm-plug support in Documentation/ide/warm-plug-howto.txt.

v2:
* Convert patch from using 'struct class_device' to use 'struct device'.
  (thanks to Kay Sievers for doing it)

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-probe.c

@@ -623,7 +623,7 @@ static void hwif_release_dev (struct device *dev)
 	complete(&hwif->gendev_rel_comp);
 }
 
-static void ide_register_port(ide_hwif_t *hwif)
+static int ide_register_port(ide_hwif_t *hwif)
 {
 	int ret;
 
@@ -639,9 +639,23 @@ static void ide_register_port(ide_hwif_t *hwif)
 	}
 	hwif->gendev.release = hwif_release_dev;
 	ret = device_register(&hwif->gendev);
-	if (ret < 0)
+	if (ret < 0) {
 		printk(KERN_WARNING "IDE: %s: device_register error: %d\n",
 			__FUNCTION__, ret);
+		goto out;
+	}
+
+	get_device(&hwif->gendev);
+
+	hwif->portdev = device_create(ide_port_class, &hwif->gendev,
+				      MKDEV(0, 0), hwif->name);
+	if (IS_ERR(hwif->portdev)) {
+		ret = PTR_ERR(hwif->portdev);
+		device_unregister(&hwif->gendev);
+	}
+	dev_set_drvdata(hwif->portdev, hwif);
+out:
+	return ret;
 }
 
 /**
@@ -1378,6 +1392,58 @@ static void ide_port_cable_detect(ide_hwif_t *hwif)
 	}
 }
 
+static ssize_t store_delete_devices(struct device *portdev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t n)
+{
+	ide_hwif_t *hwif = dev_get_drvdata(portdev);
+
+	if (strncmp(buf, "1", n))
+		return -EINVAL;
+
+	ide_port_unregister_devices(hwif);
+
+	return n;
+};
+
+static DEVICE_ATTR(delete_devices, S_IWUSR, NULL, store_delete_devices);
+
+static ssize_t store_scan(struct device *portdev,
+			  struct device_attribute *attr,
+			  const char *buf, size_t n)
+{
+	ide_hwif_t *hwif = dev_get_drvdata(portdev);
+
+	if (strncmp(buf, "1", n))
+		return -EINVAL;
+
+	ide_port_unregister_devices(hwif);
+	ide_port_scan(hwif);
+
+	return n;
+};
+
+static DEVICE_ATTR(scan, S_IWUSR, NULL, store_scan);
+
+static struct device_attribute *ide_port_attrs[] = {
+	&dev_attr_delete_devices,
+	&dev_attr_scan,
+	NULL
+};
+
+static int ide_sysfs_register_port(ide_hwif_t *hwif)
+{
+	int i, rc;
+
+	for (i = 0; ide_port_attrs[i]; i++) {
+		rc = device_create_file(hwif->portdev, ide_port_attrs[i]);
+		if (rc)
+			break;
+	}
+
+	return rc;
+}
+
 int ide_device_add_all(u8 *idx, const struct ide_port_info *d)
 {
 	ide_hwif_t *hwif, *mate = NULL;
@@ -1474,6 +1540,7 @@ int ide_device_add_all(u8 *idx, const struct ide_port_info *d)
 		hwif = &ide_hwifs[idx[i]];
 
 		if (hwif->present) {
+			ide_sysfs_register_port(hwif);
 			ide_proc_register_port(hwif);
 			ide_proc_port_register_devices(hwif);
 		}