github.com/bugraaydogar/snapd@v0.0.0-20210315170335-8c70bb858939/interfaces/builtin/i2c.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2016 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package builtin
    21  
    22  import (
    23  	"fmt"
    24  	"path/filepath"
    25  	"regexp"
    26  	"strings"
    27  
    28  	"github.com/snapcore/snapd/interfaces"
    29  	"github.com/snapcore/snapd/interfaces/apparmor"
    30  	"github.com/snapcore/snapd/interfaces/udev"
    31  	"github.com/snapcore/snapd/snap"
    32  )
    33  
    34  const i2cSummary = `allows access to specific I2C controller`
    35  
    36  const i2cBaseDeclarationSlots = `
    37    i2c:
    38      allow-installation:
    39        slot-snap-type:
    40          - gadget
    41          - core
    42      deny-auto-connection: true
    43  `
    44  
    45  const i2cConnectedPlugAppArmorPath = `
    46  # Description: Can access I2C controller
    47  
    48  %s rw,
    49  `
    50  
    51  const i2cConnectedPlugAppArmorSysfsName = `
    52  # Description: Can access I2C sysfs name
    53  
    54  /sys/bus/i2c/devices/%s/** rw,
    55  `
    56  
    57  // The type for i2c interface
    58  type i2cInterface struct{}
    59  
    60  // Getter for the name of the i2c interface
    61  func (iface *i2cInterface) Name() string {
    62  	return "i2c"
    63  }
    64  
    65  func (iface *i2cInterface) StaticInfo() interfaces.StaticInfo {
    66  	return interfaces.StaticInfo{
    67  		Summary:              i2cSummary,
    68  		BaseDeclarationSlots: i2cBaseDeclarationSlots,
    69  	}
    70  }
    71  
    72  func (iface *i2cInterface) String() string {
    73  	return iface.Name()
    74  }
    75  
    76  // Pattern to match allowed i2c device nodes. It is gonna be used to check the
    77  // validity of the path attributes in case the udev is not used for
    78  // identification
    79  var i2cControlDeviceNodePattern = regexp.MustCompile("^/dev/i2c-[0-9]+$")
    80  
    81  // Pattern to match allowed i2c sysfs names.
    82  var i2cValidSysfsName = regexp.MustCompile("^[a-zA-Z0-9_-]+$")
    83  
    84  // Check validity of the defined slot
    85  func (iface *i2cInterface) BeforePrepareSlot(slot *snap.SlotInfo) error {
    86  	sysfsName, ok := slot.Attrs["sysfs-name"].(string)
    87  	if ok {
    88  		if !i2cValidSysfsName.MatchString(sysfsName) {
    89  			return fmt.Errorf("%s sysfs-name attribute must be a valid sysfs-name", iface.Name())
    90  		}
    91  		if _, ok := slot.Attrs["path"].(string); ok {
    92  			return fmt.Errorf("%s slot can only use path or sysfs-name", iface.Name())
    93  		}
    94  		return nil
    95  	}
    96  
    97  	// Validate the path
    98  	path, ok := slot.Attrs["path"].(string)
    99  	if !ok || path == "" {
   100  		return fmt.Errorf("%s slot must have a path or sysfs-name attribute", iface.Name())
   101  	}
   102  	// XXX: this interface feeds the cleaned path into the regex and is
   103  	// left unchanged here for historical reasons. New interfaces (eg,
   104  	// like raw-volume) should instead use verifySlotPathAttribute() which
   105  	// performs additional verification.
   106  	path = filepath.Clean(path)
   107  
   108  	if !i2cControlDeviceNodePattern.MatchString(path) {
   109  		return fmt.Errorf("%s path attribute must be a valid device node", iface.Name())
   110  	}
   111  
   112  	return nil
   113  }
   114  
   115  func (iface *i2cInterface) AppArmorConnectedPlug(spec *apparmor.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
   116  
   117  	// check if sysfsName is set and if so stop after that
   118  	var sysfsName string
   119  	if err := slot.Attr("sysfs-name", &sysfsName); err == nil {
   120  		spec.AddSnippet(fmt.Sprintf(i2cConnectedPlugAppArmorSysfsName, sysfsName))
   121  		return nil
   122  	}
   123  
   124  	// do path if sysfsName is not set (they can't be set both)
   125  	var path string
   126  	if err := slot.Attr("path", &path); err != nil {
   127  		return nil
   128  	}
   129  
   130  	cleanedPath := filepath.Clean(path)
   131  	spec.AddSnippet(fmt.Sprintf(i2cConnectedPlugAppArmorPath, cleanedPath))
   132  	// Use parametric snippets to avoid no-expr-simplify side-effects.
   133  	spec.AddParametricSnippet([]string{
   134  		"/sys/devices/platform/{*,**.i2c}/i2c-" /* ###PARAM### */, "/** rw,  # Add any condensed parametric rules",
   135  	}, strings.TrimPrefix(path, "/dev/i2c-"))
   136  	return nil
   137  }
   138  
   139  func (iface *i2cInterface) UDevConnectedPlug(spec *udev.Specification, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error {
   140  	var path string
   141  	if err := slot.Attr("path", &path); err != nil {
   142  		return nil
   143  	}
   144  	spec.TagDevice(fmt.Sprintf(`KERNEL=="%s"`, strings.TrimPrefix(path, "/dev/")))
   145  	return nil
   146  }
   147  
   148  func (iface *i2cInterface) AutoConnect(*snap.PlugInfo, *snap.SlotInfo) bool {
   149  	// Allow what is allowed in the declarations
   150  	return true
   151  }
   152  
   153  func init() {
   154  	registerIface(&i2cInterface{})
   155  }