Add support for several /sys/class/sas_* classes (#453)

* Initial addition of several sysfs/class_sas* files, plus fixtures.

These parse several SAS classes from /sys/class/
  - sas_host
  - sas_device
  - sas_end_device
  - sas_expander
  - sas_port
  - sas_phy

The included fixtures include examples of all of these.

Signed-off-by: Scott Laird <scott@sigkill.org>

sysfs/class_sas_device.go

@@ -0,0 +1,209 @@
+// Copyright 2022 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build linux
+// +build linux
+
+package sysfs
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"regexp"
+
+	"github.com/prometheus/procfs/internal/util"
+)
+
+const (
+	sasDeviceClassPath    = "class/sas_device"
+	sasEndDeviceClassPath = "class/sas_end_device"
+	sasExpanderClassPath  = "class/sas_expander"
+)
+
+type SASDevice struct {
+	Name         string   // /sys/class/sas_device/<Name>
+	SASAddress   string   // /sys/class/sas_device/<Name>/sas_address
+	SASPhys      []string // /sys/class/sas_device/<Name>/device/phy-*
+	SASPorts     []string // /sys/class/sas_device/<Name>/device/ports-*
+	BlockDevices []string // /sys/class/sas_device/<Name>/device/target*/*/block/*
+}
+
+type SASDeviceClass map[string]*SASDevice
+
+var (
+	sasTargetDeviceRegexp    = regexp.MustCompile(`^target[0-9:]+$`)
+	sasTargetSubDeviceRegexp = regexp.MustCompile(`[0-9]+:.*`)
+)
+
+// sasDeviceClasses reads all of the SAS devices from a specific set
+// of /sys/class/sas*/ entries.  The sas_device, sas_end_device, and
+// sas_expander classes are all nearly identical and can be handled by the same basic code.
+
+func (fs FS) parseSASDeviceClass(dir string) (SASDeviceClass, error) {
+	path := fs.sys.Path(dir)
+
+	dirs, err := ioutil.ReadDir(path)
+	if err != nil {
+		return nil, err
+	}
+
+	sdc := make(SASDeviceClass, len(dirs))
+
+	for _, d := range dirs {
+		device, err := fs.parseSASDevice(d.Name())
+		if err != nil {
+			return nil, err
+		}
+
+		sdc[device.Name] = device
+	}
+
+	return sdc, nil
+}
+
+// SASDeviceClass parses devices in /sys/class/sas_device.
+func (fs FS) SASDeviceClass() (SASDeviceClass, error) {
+	return fs.parseSASDeviceClass(sasDeviceClassPath)
+}
+
+// SASEndDeviceClass parses devices in /sys/class/sas_end_device.
+// This is a subset of sas_device, and excludes expanders.
+func (fs FS) SASEndDeviceClass() (SASDeviceClass, error) {
+	return fs.parseSASDeviceClass(sasEndDeviceClassPath)
+}
+
+// SASExpanderClass parses devices in /sys/class/sas_expander.
+// This is a subset of sas_device, but only includes expanders.
+func (fs FS) SASExpanderClass() (SASDeviceClass, error) {
+	return fs.parseSASDeviceClass(sasExpanderClassPath)
+}
+
+// Parse a single sas_device.  This uses /sys/class/sas_device, as
+// it's a superset of the other two directories so there's no reason
+// to plumb the path through to here.
+func (fs FS) parseSASDevice(name string) (*SASDevice, error) {
+	device := SASDevice{Name: name}
+
+	devicepath := fs.sys.Path(filepath.Join(sasDeviceClassPath, name, "device"))
+
+	dirs, err := ioutil.ReadDir(devicepath)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, d := range dirs {
+		if sasPhyDeviceRegexp.MatchString(d.Name()) {
+			device.SASPhys = append(device.SASPhys, d.Name())
+		}
+		if sasPortDeviceRegexp.MatchString(d.Name()) {
+			device.SASPorts = append(device.SASPorts, d.Name())
+		}
+	}
+
+	address := fs.sys.Path(sasDeviceClassPath, name, "sas_address")
+	value, err := util.SysReadFile(address)
+	if err != nil {
+		return nil, err
+	}
+	device.SASAddress = value
+
+	device.BlockDevices, err = fs.blockSASDeviceBlockDevices(name)
+	if err != nil {
+		return nil, err
+	}
+
+	return &device, nil
+}
+
+// Identify block devices that map to a specific SAS Device
+// This info comes from (for example)
+// /sys/class/sas_device/end_device-11:2/device/target11:0:0/11:0:0:0/block/sdp
+//
+// To find that, we have to look in the device directory for target$X
+// subdirs, then specific subdirs of $X, then read from directory
+// names in the 'block/' subdirectory under that.  This really
+// shouldn't be this hard.
+func (fs FS) blockSASDeviceBlockDevices(name string) ([]string, error) {
+	var devices []string
+
+	devicepath := fs.sys.Path(filepath.Join(sasDeviceClassPath, name, "device"))
+
+	dirs, err := ioutil.ReadDir(devicepath)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, d := range dirs {
+		if sasTargetDeviceRegexp.MatchString(d.Name()) {
+			targetdir := d.Name()
+
+			subtargets, err := ioutil.ReadDir(filepath.Join(devicepath, targetdir))
+			if err != nil {
+				return nil, err
+			}
+
+			for _, targetsubdir := range subtargets {
+
+				if !sasTargetSubDeviceRegexp.MatchString(targetsubdir.Name()) {
+					// need to skip 'power', 'subsys', etc.
+					continue
+				}
+
+				blocks, err := ioutil.ReadDir(filepath.Join(devicepath, targetdir, targetsubdir.Name(), "block"))
+				if err != nil {
+					if os.IsNotExist(err) {
+						continue
+					} else {
+						return nil, err
+					}
+				}
+
+				for _, blockdevice := range blocks {
+					devices = append(devices, blockdevice.Name())
+				}
+			}
+		}
+	}
+
+	return devices, nil
+}
+
+// GetByName returns the SASDevice with the provided name.
+func (sdc *SASDeviceClass) GetByName(name string) *SASDevice {
+	return (*sdc)[name]
+}
+
+// GetByPhy finds the SASDevice that contains the provided PHY name.
+func (sdc *SASDeviceClass) GetByPhy(name string) *SASDevice {
+	for _, d := range *sdc {
+		for _, p := range d.SASPhys {
+			if p == name {
+				return d
+			}
+		}
+	}
+	return nil
+}
+
+// GetByPort finds the SASDevice that contains the provided SAS Port name.
+func (sdc *SASDeviceClass) GetByPort(name string) *SASDevice {
+	for _, d := range *sdc {
+		for _, p := range d.SASPorts {
+			if p == name {
+				return d
+			}
+		}
+	}
+	return nil
+}