blog/data/2013-01-14-hw-autoinstall-modalias.txt

   1 Title: Modalias strings - a practical way to map "stuff" to hardware
   2 Tags: english, debian
   3 Date: 2013-01-14 11:10
   4
   5 <p>While looking into how to look up Debian packages based on hardware
   6 information, to find the packages that support a given piece of
   7 hardware, I refreshed my memory regarding modalias values, and decided
   8 to document the details.  Here are my findings so far, also available
   9 in
  10 <a href="http://anonscm.debian.org/viewvc/debian-edu/trunk/src/hw-support-handler/">the
  11 Debian Edu subversion repository</a>:
  12
  13 <p><strong>Modalias decoded</strong></p>
  14
  15 <p>This document try to explain what the different types of modalias
  16 values stands for.  It is in part based on information from
  17 &lt;URL: <a href="https://wiki.archlinux.org/index.php/Modalias">https://wiki.archlinux.org/index.php/Modalias</a> &gt;,
  18 &lt;URL: <a href="http://unix.stackexchange.com/questions/26132/how-to-assign-usb-driver-to-device">http://unix.stackexchange.com/questions/26132/how-to-assign-usb-driver-to-device</a> &gt;,
  19 &lt;URL: <a href="http://code.metager.de/source/history/linux/stable/scripts/mod/file2alias.c">http://code.metager.de/source/history/linux/stable/scripts/mod/file2alias.c</a> &gt; and
  20 &lt;URL: <a href="http://cvs.savannah.gnu.org/viewvc/dmidecode/dmidecode.c?root=dmidecode&view=markup">http://cvs.savannah.gnu.org/viewvc/dmidecode/dmidecode.c?root=dmidecode&view=markup</a> &gt;.
  21
  22 <p><strong>PCI subtype</strong></p>
  23
  24 <p>A typical PCI entry can look like this.  This is an Intel Host
  25 Bridge memory controller:</p>
  26
  27 <p><blockquote>
  28 pci:v00008086d00002770sv00001028sd000001ADbc06sc00i00
  29 </blockquote></p>
  30
  31 <p>This represent these values:</p>
  32
  33 <pre>
  34  v   00008086  (vendor)
  35  d   00002770  (device)
  36  sv  00001028  (subvendor)
  37  sd  000001AD  (subdevice)
  38  bc  06        (bus class)
  39  sc  00        (bus subclass)
  40  i   00        (interface)
  41 </pre>
  42
  43 <p>The vendor/device values are the same values outputted from 'lspci
  44 -n' as 8086:2770.  The bus class/subclass is also shown by lspci as
  45 0600.  The 0600 class is a host bridge.  Other useful bus values are
  46 0300 (VGA compatible card) and 0200 (Ethernet controller).</p>
  47
  48 <p>Not sure how to figure out the interface value, nor what it
  49 means.</p>
  50
  51 <p><strong>USB subtype</strong></p>
  52
  53 <p>Some typical USB entries can look like this.  This is an internal
  54 USB hub in a laptop:</p>
  55
  56 <p><blockquote>
  57 usb:v1D6Bp0001d0206dc09dsc00dp00ic09isc00ip00
  58 </blockquote></p>
  59
  60 <p>Here is the values included in this alias:</p>
  61
  62 <pre>
  63  v    1D6B  (device vendor)
  64  p    0001  (device product)
  65  d    0206  (bcddevice)
  66  dc     09  (device class)
  67  dsc    00  (device subclass)
  68  dp     00  (device protocol)
  69  ic     09  (interface class)
  70  isc    00  (interface subclass)
  71  ip     00  (interface protocol)
  72 </pre>
  73
  74 <p>The 0900 device class/subclass means hub.  Some times the relevant
  75 class is in the interface class section.  For a simple USB web camera,
  76 these alias entries show up:</p>
  77
  78 <p><blockquote>
  79 usb:v0AC8p3420d5000dcEFdsc02dp01ic01isc01ip00
  80 <br>usb:v0AC8p3420d5000dcEFdsc02dp01ic01isc02ip00
  81 <br>usb:v0AC8p3420d5000dcEFdsc02dp01ic0Eisc01ip00
  82 <br>usb:v0AC8p3420d5000dcEFdsc02dp01ic0Eisc02ip00
  83 </blockquote></p>
  84
  85 <p>Interface class 0E01 is video control, 0E02 is video streaming (aka
  86 camera), 0101 is audio control device and 0102 is audio streaming (aka
  87 microphone).  Thus this is a camera with microphone included.</p>
  88
  89 <p><strong>ACPI subtype</strong></p>
  90
  91 <p>The ACPI type is used for several non-PCI/USB stuff.  This is an IR
  92 receiver in a Thinkpad X40:</p>
  93
  94 <p><blockquote>
  95 acpi:IBM0071:PNP0511:
  96 </blockquote></p>
  97
  98 <p>The values between the colons are IDs.</p>
  99
 100 <p><strong>DMI subtype</strong></p>
 101
 102 <p>The DMI table contain lots of information about the computer case
 103 and model.  This is an entry for a IBM Thinkpad X40, fetched from
 104 /sys/devices/virtual/dmi/id/modalias:</p>
 105
 106 <p><blockquote>
 107 dmi:bvnIBM:bvr1UETB6WW(1.66):bd06/15/2005:svnIBM:pn2371H4G:pvrThinkPadX40:rvnIBM:rn2371H4G:rvrNotAvailable:cvnIBM:ct10:cvrNotAvailable:
 108 </blockquote></p>
 109
 110 <p>The values present are</p>
 111
 112 <pre>
 113  bvn  IBM            (BIOS vendor)
 114  bvr  1UETB6WW(1.66) (BIOS version)
 115  bd   06/15/2005     (BIOS date)
 116  svn  IBM            (system vendor)
 117  pn   2371H4G        (product name)
 118  pvr  ThinkPadX40    (product version)
 119  rvn  IBM            (board vendor)
 120  rn   2371H4G        (board name)
 121  rvr  NotAvailable   (board version)
 122  cvn  IBM            (chassis vendor)
 123  ct   10             (chassis type)
 124  cvr  NotAvailable   (chassis version)
 125 </pre>
 126
 127 <p>The chassis type 10 is Notebook.  Other interesting values can be
 128 found in the dmidecode source:</p>
 129
 130 <pre>
 131   3 Desktop
 132   4 Low Profile Desktop
 133   5 Pizza Box
 134   6 Mini Tower
 135   7 Tower
 136   8 Portable
 137   9 Laptop
 138  10 Notebook
 139  11 Hand Held
 140  12 Docking Station
 141  13 All In One
 142  14 Sub Notebook
 143  15 Space-saving
 144  16 Lunch Box
 145  17 Main Server Chassis
 146  18 Expansion Chassis
 147  19 Sub Chassis
 148  20 Bus Expansion Chassis
 149  21 Peripheral Chassis
 150  22 RAID Chassis
 151  23 Rack Mount Chassis
 152  24 Sealed-case PC
 153  25 Multi-system
 154  26 CompactPCI
 155  27 AdvancedTCA
 156  28 Blade
 157  29 Blade Enclosing
 158 </pre>
 159
 160 <p>The chassis type values are not always accurately set in the DMI
 161 table.  For example my home server is a tower, but the DMI modalias
 162 claim it is a desktop.</p>
 163
 164 <p><strong>SerIO subtype</strong></p>
 165
 166 <p>This type is used for PS/2 mouse plugs.  One example is from my
 167 test machine:</p>
 168
 169 <p><blockquote>
 170 serio:ty01pr00id00ex00
 171 </blockquote></p>
 172
 173 <p>The values present are</p>
 174
 175 <pre>
 176   ty  01  (type)
 177   pr  00  (prototype)
 178   id  00  (id)
 179   ex  00  (extra)
 180 </pre>
 181
 182 <p>This type is supported by the psmouse driver.  I am not sure what
 183 the valid values are.</p>
 184
 185 <p><strong>Other subtypes</strong></p>
 186
 187 <p>There are heaps of other modalias subtypes according to
 188 file2alias.c.  There is the rest of the list from that source: amba,
 189 ap, bcma, ccw, css, eisa, hid, i2c, ieee1394, input, ipack, isapnp,
 190 mdio, of, parisc, pcmcia, platform, scsi, sdio, spi, ssb, vio, virtio,
 191 vmbus, x86cpu and zorro.  I did not spend time documenting all of
 192 these, as they do not seem relevant for my intended use with mapping
 193 hardware to packages when new stuff is inserted during run time.</p>
 194
 195 <p><strong>Looking up kernel modules using modalias values</strong></p>
 196
 197 <p>To check which kernel modules provide support for a given modalias,
 198 one can use the following shell script:</p>
 199
 200 <pre>
 201   for id in $(cat $(find /sys -name modalias)|sort -u); do \
 202     echo "$id" ; \
 203     /sbin/modprobe --show-depends "$id"|sed 's/^/  /' ; \
 204   done
 205 </pre>
 206
 207 <p>The output can look like this (only the first few entries as the
 208 list is very long on my test machine):</p>
 209
 210 <pre>
 211   acpi:ACPI0003:
 212     insmod /lib/modules/2.6.32-5-686/kernel/drivers/acpi/ac.ko
 213   acpi:device:
 214   FATAL: Module acpi:device: not found.
 215   acpi:IBM0068:
 216     insmod /lib/modules/2.6.32-5-686/kernel/drivers/char/nvram.ko
 217     insmod /lib/modules/2.6.32-5-686/kernel/drivers/leds/led-class.ko
 218     insmod /lib/modules/2.6.32-5-686/kernel/net/rfkill/rfkill.ko
 219     insmod /lib/modules/2.6.32-5-686/kernel/drivers/platform/x86/thinkpad_acpi.ko
 220   acpi:IBM0071:PNP0511:
 221     insmod /lib/modules/2.6.32-5-686/kernel/lib/crc-ccitt.ko
 222     insmod /lib/modules/2.6.32-5-686/kernel/net/irda/irda.ko
 223     insmod /lib/modules/2.6.32-5-686/kernel/drivers/net/irda/nsc-ircc.ko
 224   [...]
 225 </pre>
 226
 227 <p>If you want to help implementing a system to let us propose what
 228 packages to install when new hardware is plugged into a Debian
 229 machine, please send me an email or talk to me on
 230 <a href="irc://irc.debian.org/%23debian-devel">#debian-devel</a>.</p>