feat: make disk utils read subsystem information from the /sys/block

This way it will be possible to tell what kind of block device is that.

Signed-off-by: Artem Chernyshev <artem.chernyshev@talos-systems.com>

blockdevice/util/disk/disks.go

@@ -90,6 +90,8 @@ type Disk struct {
 	Type Type
 	// BusPath PCI bus path.
 	BusPath string
+	// SubSystem is the dest path of symlink /sys/block/<dev>/subsystem.
+	SubSystem string
 	// ReadOnly indicates that the kernel has marked this disk as read-only.
 	ReadOnly bool
 }
@@ -209,7 +211,7 @@ func Get(dev string) *Disk {
 		readOnlyBool = true
 	}
 
-	return &Disk{
+	disk := &Disk{
 		DeviceName: fmt.Sprintf("/dev/%s", dev),
 		Size:       size,
 		Model:      readFile(sysblock, dev, "device/model"),
@@ -222,6 +224,13 @@ func Get(dev string) *Disk {
 		BusPath:    busPath,
 		ReadOnly:   readOnlyBool,
 	}
+
+	path, err := filepath.EvalSymlinks(filepath.Join(sysblock, dev, "subsystem"))
+	if err == nil {
+		disk.SubSystem = path
+	}
+
+	return disk
 }
 
 // Find disk matching provided spec.

blockdevice/util/disk/disks_test.go

@@ -26,6 +26,7 @@ func (suite *DisksSuite) TestDisks() {
 		for _, d := range disks {
 			suite.Require().NotEmpty(d.DeviceName)
 			suite.Require().NotEmpty(d.Model)
+			suite.Require().NotEmpty(d.SubSystem)
 		}
 	}
 }