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, isenkram
   3 Date: 2013-01-14 11:20
   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>The modalias entries for a given Linux machine can be found using
  23 this shell script:</p>
  24
  25 <pre>
  26 find /sys -name modalias -print0 | xargs -0 cat | sort -u
  27 </pre>
  28
  29 <p>The supported modalias globs for a given kernel module can be found
  30 using modinfo:</p>
  31
  32 <pre>
  33 % /sbin/modinfo psmouse | grep alias:
  34 alias:          serio:ty05pr*id*ex*
  35 alias:          serio:ty01pr*id*ex*
  36 %
  37 </pre>
  38
  39 <p><strong>PCI subtype</strong></p>
  40
  41 <p>A typical PCI entry can look like this.  This is an Intel Host
  42 Bridge memory controller:</p>
  43
  44 <p><blockquote>
  45 pci:v00008086d00002770sv00001028sd000001ADbc06sc00i00
  46 </blockquote></p>
  47
  48 <p>This represent these values:</p>
  49
  50 <pre>
  51  v   00008086  (vendor)
  52  d   00002770  (device)
  53  sv  00001028  (subvendor)
  54  sd  000001AD  (subdevice)
  55  bc  06        (bus class)
  56  sc  00        (bus subclass)
  57  i   00        (interface)
  58 </pre>
  59
  60 <p>The vendor/device values are the same values outputted from 'lspci
  61 -n' as 8086:2770.  The bus class/subclass is also shown by lspci as
  62 0600.  The 0600 class is a host bridge.  Other useful bus values are
  63 0300 (VGA compatible card) and 0200 (Ethernet controller).</p>
  64
  65 <p>Not sure how to figure out the interface value, nor what it
  66 means.</p>
  67
  68 <p><strong>USB subtype</strong></p>
  69
  70 <p>Some typical USB entries can look like this.  This is an internal
  71 USB hub in a laptop:</p>
  72
  73 <p><blockquote>
  74 usb:v1D6Bp0001d0206dc09dsc00dp00ic09isc00ip00
  75 </blockquote></p>
  76
  77 <p>Here is the values included in this alias:</p>
  78
  79 <pre>
  80  v    1D6B  (device vendor)
  81  p    0001  (device product)
  82  d    0206  (bcddevice)
  83  dc     09  (device class)
  84  dsc    00  (device subclass)
  85  dp     00  (device protocol)
  86  ic     09  (interface class)
  87  isc    00  (interface subclass)
  88  ip     00  (interface protocol)
  89 </pre>
  90
  91 <p>The 0900 device class/subclass means hub.  Some times the relevant
  92 class is in the interface class section.  For a simple USB web camera,
  93 these alias entries show up:</p>
  94
  95 <p><blockquote>
  96 usb:v0AC8p3420d5000dcEFdsc02dp01ic01isc01ip00
  97 <br>usb:v0AC8p3420d5000dcEFdsc02dp01ic01isc02ip00
  98 <br>usb:v0AC8p3420d5000dcEFdsc02dp01ic0Eisc01ip00
  99 <br>usb:v0AC8p3420d5000dcEFdsc02dp01ic0Eisc02ip00
 100 </blockquote></p>
 101
 102 <p>Interface class 0E01 is video control, 0E02 is video streaming (aka
 103 camera), 0101 is audio control device and 0102 is audio streaming (aka
 104 microphone).  Thus this is a camera with microphone included.</p>
 105
 106 <p><strong>ACPI subtype</strong></p>
 107
 108 <p>The ACPI type is used for several non-PCI/USB stuff.  This is an IR
 109 receiver in a Thinkpad X40:</p>
 110
 111 <p><blockquote>
 112 acpi:IBM0071:PNP0511:
 113 </blockquote></p>
 114
 115 <p>The values between the colons are IDs.</p>
 116
 117 <p><strong>DMI subtype</strong></p>
 118
 119 <p>The DMI table contain lots of information about the computer case
 120 and model.  This is an entry for a IBM Thinkpad X40, fetched from
 121 /sys/devices/virtual/dmi/id/modalias:</p>
 122
 123 <p><blockquote>
 124 dmi:bvnIBM:bvr1UETB6WW(1.66):bd06/15/2005:svnIBM:pn2371H4G:pvrThinkPadX40:rvnIBM:rn2371H4G:rvrNotAvailable:cvnIBM:ct10:cvrNotAvailable:
 125 </blockquote></p>
 126
 127 <p>The values present are</p>
 128
 129 <pre>
 130  bvn  IBM            (BIOS vendor)
 131  bvr  1UETB6WW(1.66) (BIOS version)
 132  bd   06/15/2005     (BIOS date)
 133  svn  IBM            (system vendor)
 134  pn   2371H4G        (product name)
 135  pvr  ThinkPadX40    (product version)
 136  rvn  IBM            (board vendor)
 137  rn   2371H4G        (board name)
 138  rvr  NotAvailable   (board version)
 139  cvn  IBM            (chassis vendor)
 140  ct   10             (chassis type)
 141  cvr  NotAvailable   (chassis version)
 142 </pre>
 143
 144 <p>The chassis type 10 is Notebook.  Other interesting values can be
 145 found in the dmidecode source:</p>
 146
 147 <pre>
 148   3 Desktop
 149   4 Low Profile Desktop
 150   5 Pizza Box
 151   6 Mini Tower
 152   7 Tower
 153   8 Portable
 154   9 Laptop
 155  10 Notebook
 156  11 Hand Held
 157  12 Docking Station
 158  13 All In One
 159  14 Sub Notebook
 160  15 Space-saving
 161  16 Lunch Box
 162  17 Main Server Chassis
 163  18 Expansion Chassis
 164  19 Sub Chassis
 165  20 Bus Expansion Chassis
 166  21 Peripheral Chassis
 167  22 RAID Chassis
 168  23 Rack Mount Chassis
 169  24 Sealed-case PC
 170  25 Multi-system
 171  26 CompactPCI
 172  27 AdvancedTCA
 173  28 Blade
 174  29 Blade Enclosing
 175 </pre>
 176
 177 <p>The chassis type values are not always accurately set in the DMI
 178 table.  For example my home server is a tower, but the DMI modalias
 179 claim it is a desktop.</p>
 180
 181 <p><strong>SerIO subtype</strong></p>
 182
 183 <p>This type is used for PS/2 mouse plugs.  One example is from my
 184 test machine:</p>
 185
 186 <p><blockquote>
 187 serio:ty01pr00id00ex00
 188 </blockquote></p>
 189
 190 <p>The values present are</p>
 191
 192 <pre>
 193   ty  01  (type)
 194   pr  00  (prototype)
 195   id  00  (id)
 196   ex  00  (extra)
 197 </pre>
 198
 199 <p>This type is supported by the psmouse driver.  I am not sure what
 200 the valid values are.</p>
 201
 202 <p><strong>Other subtypes</strong></p>
 203
 204 <p>There are heaps of other modalias subtypes according to
 205 file2alias.c.  There is the rest of the list from that source: amba,
 206 ap, bcma, ccw, css, eisa, hid, i2c, ieee1394, input, ipack, isapnp,
 207 mdio, of, parisc, pcmcia, platform, scsi, sdio, spi, ssb, vio, virtio,
 208 vmbus, x86cpu and zorro.  I did not spend time documenting all of
 209 these, as they do not seem relevant for my intended use with mapping
 210 hardware to packages when new stuff is inserted during run time.</p>
 211
 212 <p><strong>Looking up kernel modules using modalias values</strong></p>
 213
 214 <p>To check which kernel modules provide support for a given modalias,
 215 one can use the following shell script:</p>
 216
 217 <pre>
 218   for id in $(find /sys -name modalias -print0 | xargs -0 cat | sort -u); do \
 219     echo "$id" ; \
 220     /sbin/modprobe --show-depends "$id"|sed 's/^/  /' ; \
 221   done
 222 </pre>
 223
 224 <p>The output can look like this (only the first few entries as the
 225 list is very long on my test machine):</p>
 226
 227 <pre>
 228   acpi:ACPI0003:
 229     insmod /lib/modules/2.6.32-5-686/kernel/drivers/acpi/ac.ko
 230   acpi:device:
 231   FATAL: Module acpi:device: not found.
 232   acpi:IBM0068:
 233     insmod /lib/modules/2.6.32-5-686/kernel/drivers/char/nvram.ko
 234     insmod /lib/modules/2.6.32-5-686/kernel/drivers/leds/led-class.ko
 235     insmod /lib/modules/2.6.32-5-686/kernel/net/rfkill/rfkill.ko
 236     insmod /lib/modules/2.6.32-5-686/kernel/drivers/platform/x86/thinkpad_acpi.ko
 237   acpi:IBM0071:PNP0511:
 238     insmod /lib/modules/2.6.32-5-686/kernel/lib/crc-ccitt.ko
 239     insmod /lib/modules/2.6.32-5-686/kernel/net/irda/irda.ko
 240     insmod /lib/modules/2.6.32-5-686/kernel/drivers/net/irda/nsc-ircc.ko
 241   [...]
 242 </pre>
 243
 244 <p>If you want to help implementing a system to let us propose what
 245 packages to install when new hardware is plugged into a Debian
 246 machine, please send me an email or talk to me on
 247 <a href="irc://irc.debian.org/%23debian-devel">#debian-devel</a>.</p>
 248
 249 <p><strong>Update 2013-01-15:</strong> Rewrite "cat $(find ...)" to
 250 "find ... -print0 | xargs -0 cat" to make sure it handle directories
 251 in /sys/ with space in them.</p>