[systemd-devel] [PATCH] udev: build by-path identifiers for ATA

[David Milburn]

Patch to build by-path identifiers for ATA devices.

# pwd
/dev/disk/by-path

# ll
total 0
lrwxrwxrwx. 1 root root  9 Sep  4 10:02 pci-0000:00:1f.2-ata-2 -> ../../sr0
lrwxrwxrwx. 1 root root  9 Sep  4 10:02 pci-0000:00:1f.2-ata-3 -> ../../sdd
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:00:1f.2-ata-3-part1 -> ../../sdd1
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:00:1f.2-ata-3-part2 -> ../../sdd2
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:00:1f.2-ata-3-part3 -> ../../sdd3
lrwxrwxrwx. 1 root root  9 Sep  4 10:02 pci-0000:03:00.0-ata-4 -> ../../sda
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:03:00.0-ata-4-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:03:00.0-ata-4-part2 -> ../../sda2
lrwxrwxrwx. 1 root root  9 Sep  4 10:02 pci-0000:08:00.0-ata-1 -> ../../sdc
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:08:00.0-ata-1-part1 -> ../../sdc1
lrwxrwxrwx. 1 root root 10 Sep  4 10:02 pci-0000:08:00.0-ata-1-part2 -> ../../sdc2

--- src/udev/udev-builtin-path_id.c.systemd-208-20.el7	2015-09-03 10:19:20.385434297 -0500
+++ src/udev/udev-builtin-path_id.c	2015-09-04 10:05:22.039260808 -0500
@@ -217,6 +217,38 @@ out:
         return parent;
 }
 
+static struct udev_device *handle_scsi_ata(struct udev_device *parent, char **path)
+{
+	struct udev *udev  = udev_device_get_udev(parent);
+	struct udev_device *targetdev;
+	struct udev_device *target_parent;
+	struct udev_device *atadev;
+	const char *port_no;
+
+	targetdev = udev_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_host");
+	if (targetdev == NULL)
+		return NULL;
+
+	target_parent = udev_device_get_parent(targetdev);
+	if (target_parent == NULL)
+		return NULL;
+
+	atadev = udev_device_new_from_subsystem_sysname(udev, "ata_port",
+							udev_device_get_sysname(target_parent));
+	if (atadev == NULL)
+		return NULL;
+
+	port_no = udev_device_get_sysattr_value(atadev, "port_no");
+	if (port_no == NULL) {
+		parent = NULL;
+		goto out;
+	}
+	path_prepend(path, "ata-%s", port_no);
+out:
+        udev_device_unref(atadev);
+        return parent;
+}
+
 static struct udev_device *handle_scsi_default(struct udev_device *parent, char **path)
 {
         struct udev_device *hostdev;
@@ -374,20 +406,9 @@ static struct udev_device *handle_scsi(s
                 goto out;
         }
 
-        /*
-         * We do not support the ATA transport class, it uses global counters
-         * to name the ata devices which numbers spread across multiple
-         * controllers.
-         *
-         * The real link numbers are not exported. Also, possible chains of ports
-         * behind port multipliers cannot be composed that way.
-         *
-         * Until all that is solved at the kernel level, there are no by-path/
-         * links for ATA devices.
-         */
         if (strstr(name, "/ata") != NULL) {
-                parent = NULL;
-                goto out;
+		parent = handle_scsi_ata(parent, path);
+		goto out;
         }
 
         if (strstr(name, "/vmbus_") != NULL) {