2018-11-09 02:24:15 +03:00
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.. _magicnumbers:
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2016-09-21 23:18:36 +03:00
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Linux magic numbers
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===================
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2005-04-17 02:20:36 +04:00
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This file is a registry of magic numbers which are in use. When you
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add a magic number to a structure, you should also add it to this
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file, since it is best if the magic numbers used by various structures
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are unique.
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2016-09-21 23:18:36 +03:00
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It is a **very** good idea to protect kernel data structures with magic
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2005-04-17 02:20:36 +04:00
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numbers. This allows you to check at run time whether (a) a structure
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has been clobbered, or (b) you've passed the wrong structure to a
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routine. This last is especially useful --- particularly when you are
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passing pointers to structures via a void * pointer. The tty code,
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for example, does this frequently to pass driver-specific and line
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discipline-specific structures back and forth.
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2018-03-23 10:32:31 +03:00
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The way to use magic numbers is to declare them at the beginning of
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2016-09-21 23:18:36 +03:00
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the structure, like so::
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2016-09-21 23:18:36 +03:00
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struct tty_ldisc {
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int magic;
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...
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};
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2005-04-17 02:20:36 +04:00
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Please follow this discipline when you are adding future enhancements
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to the kernel! It has saved me countless hours of debugging,
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especially in the screwy cases where an array has been overrun and
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structures following the array have been overwritten. Using this
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discipline, these cases get detected quickly and safely.
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2016-09-21 23:18:36 +03:00
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Changelog::
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2005-04-17 02:20:36 +04:00
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Theodore Ts'o
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31 Mar 94
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2016-09-21 23:18:36 +03:00
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The magic table is current to Linux 2.1.55.
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2005-04-17 02:20:36 +04:00
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Michael Chastain
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<mailto:mec@shout.net>
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22 Sep 1997
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2016-09-21 23:18:36 +03:00
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Now it should be up to date with Linux 2.1.112. Because
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we are in feature freeze time it is very unlikely that
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something will change before 2.2.x. The entries are
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sorted by number field.
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Krzysztof G. Baranowski
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<mailto: kgb@knm.org.pl>
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29 Jul 1998
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2016-09-21 23:18:36 +03:00
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Updated the magic table to Linux 2.5.45. Right over the feature freeze,
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but it is possible that some new magic numbers will sneak into the
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kernel before 2.6.x yet.
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2005-04-17 02:20:36 +04:00
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Petr Baudis
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<pasky@ucw.cz>
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03 Nov 2002
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2016-09-21 23:18:36 +03:00
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Updated the magic table to Linux 2.5.74.
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2005-04-17 02:20:36 +04:00
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Fabian Frederick
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<ffrederick@users.sourceforge.net>
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09 Jul 2003
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2016-09-21 23:18:36 +03:00
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===================== ================ ======================== ==========================================
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Magic Name Number Structure File
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===================== ================ ======================== ==========================================
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PG_MAGIC 'P' pg_{read,write}_hdr ``include/linux/pg.h``
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CMAGIC 0x0111 user ``include/linux/a.out.h``
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MKISS_DRIVER_MAGIC 0x04bf mkiss_channel ``drivers/net/mkiss.h``
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HDLC_MAGIC 0x239e n_hdlc ``drivers/char/n_hdlc.c``
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APM_BIOS_MAGIC 0x4101 apm_user ``arch/x86/kernel/apm_32.c``
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DB_MAGIC 0x4442 fc_info ``drivers/net/iph5526_novram.c``
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DL_MAGIC 0x444d fc_info ``drivers/net/iph5526_novram.c``
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FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h``
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FF_MAGIC 0x4646 fc_info ``drivers/net/iph5526_novram.c``
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PTY_MAGIC 0x5001 ``drivers/char/pty.c``
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PPP_MAGIC 0x5002 ppp ``include/linux/if_pppvar.h``
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SSTATE_MAGIC 0x5302 serial_state ``include/linux/serial.h``
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SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h``
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STRIP_MAGIC 0x5303 strip ``drivers/net/strip.c``
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SIXPACK_MAGIC 0x5304 sixpack ``drivers/net/hamradio/6pack.h``
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AX25_MAGIC 0x5316 ax_disp ``drivers/net/mkiss.h``
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TTY_MAGIC 0x5401 tty_struct ``include/linux/tty.h``
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MGSL_MAGIC 0x5401 mgsl_info ``drivers/char/synclink.c``
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TTY_DRIVER_MAGIC 0x5402 tty_driver ``include/linux/tty_driver.h``
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MGSLPC_MAGIC 0x5402 mgslpc_info ``drivers/char/pcmcia/synclink_cs.c``
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USB_SERIAL_MAGIC 0x6702 usb_serial ``drivers/usb/serial/usb-serial.h``
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FULL_DUPLEX_MAGIC 0x6969 ``drivers/net/ethernet/dec/tulip/de2104x.c``
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USB_BLUETOOTH_MAGIC 0x6d02 usb_bluetooth ``drivers/usb/class/bluetty.c``
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RFCOMM_TTY_MAGIC 0x6d02 ``net/bluetooth/rfcomm/tty.c``
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USB_SERIAL_PORT_MAGIC 0x7301 usb_serial_port ``drivers/usb/serial/usb-serial.h``
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CG_MAGIC 0x00090255 ufs_cylinder_group ``include/linux/ufs_fs.h``
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LSEMAGIC 0x05091998 lse ``drivers/fc4/fc.c``
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RIEBL_MAGIC 0x09051990 ``drivers/net/atarilance.c``
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NBD_REQUEST_MAGIC 0x12560953 nbd_request ``include/linux/nbd.h``
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RED_MAGIC2 0x170fc2a5 (any) ``mm/slab.c``
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BAYCOM_MAGIC 0x19730510 baycom_state ``drivers/net/baycom_epp.c``
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ISDN_X25IFACE_MAGIC 0x1e75a2b9 isdn_x25iface_proto_data ``drivers/isdn/isdn_x25iface.h``
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ECP_MAGIC 0x21504345 cdkecpsig ``include/linux/cdk.h``
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LSOMAGIC 0x27091997 lso ``drivers/fc4/fc.c``
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LSMAGIC 0x2a3b4d2a ls ``drivers/fc4/fc.c``
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WANPIPE_MAGIC 0x414C4453 sdla_{dump,exec} ``include/linux/wanpipe.h``
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CS_CARD_MAGIC 0x43525553 cs_card ``sound/oss/cs46xx.c``
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LABELCL_MAGIC 0x4857434c labelcl_info_s ``include/asm/ia64/sn/labelcl.h``
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ISDN_ASYNC_MAGIC 0x49344C01 modem_info ``include/linux/isdn.h``
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CTC_ASYNC_MAGIC 0x49344C01 ctc_tty_info ``drivers/s390/net/ctctty.c``
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ISDN_NET_MAGIC 0x49344C02 isdn_net_local_s ``drivers/isdn/i4l/isdn_net_lib.h``
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SAVEKMSG_MAGIC2 0x4B4D5347 savekmsg ``arch/*/amiga/config.c``
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CS_STATE_MAGIC 0x4c4f4749 cs_state ``sound/oss/cs46xx.c``
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SLAB_C_MAGIC 0x4f17a36d kmem_cache ``mm/slab.c``
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COW_MAGIC 0x4f4f4f4d cow_header_v1 ``arch/um/drivers/ubd_user.c``
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I810_CARD_MAGIC 0x5072696E i810_card ``sound/oss/i810_audio.c``
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TRIDENT_CARD_MAGIC 0x5072696E trident_card ``sound/oss/trident.c``
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ROUTER_MAGIC 0x524d4157 wan_device [in ``wanrouter.h`` pre 3.9]
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SAVEKMSG_MAGIC1 0x53415645 savekmsg ``arch/*/amiga/config.c``
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GDA_MAGIC 0x58464552 gda ``arch/mips/include/asm/sn/gda.h``
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RED_MAGIC1 0x5a2cf071 (any) ``mm/slab.c``
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EEPROM_MAGIC_VALUE 0x5ab478d2 lanai_dev ``drivers/atm/lanai.c``
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HDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state ``include/linux/hdlcdrv.h``
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PCXX_MAGIC 0x5c6df104 channel ``drivers/char/pcxx.h``
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KV_MAGIC 0x5f4b565f kernel_vars_s ``arch/mips/include/asm/sn/klkernvars.h``
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I810_STATE_MAGIC 0x63657373 i810_state ``sound/oss/i810_audio.c``
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TRIDENT_STATE_MAGIC 0x63657373 trient_state ``sound/oss/trident.c``
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M3_CARD_MAGIC 0x646e6f50 m3_card ``sound/oss/maestro3.c``
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FW_HEADER_MAGIC 0x65726F66 fw_header ``drivers/atm/fore200e.h``
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SLOT_MAGIC 0x67267321 slot ``drivers/hotplug/cpqphp.h``
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SLOT_MAGIC 0x67267322 slot ``drivers/hotplug/acpiphp.h``
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LO_MAGIC 0x68797548 nbd_device ``include/linux/nbd.h``
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M3_STATE_MAGIC 0x734d724d m3_state ``sound/oss/maestro3.c``
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VMALLOC_MAGIC 0x87654320 snd_alloc_track ``sound/core/memory.c``
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KMALLOC_MAGIC 0x87654321 snd_alloc_track ``sound/core/memory.c``
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PWC_MAGIC 0x89DC10AB pwc_device ``drivers/usb/media/pwc.h``
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NBD_REPLY_MAGIC 0x96744668 nbd_reply ``include/linux/nbd.h``
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ENI155_MAGIC 0xa54b872d midway_eprom ``drivers/atm/eni.h``
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CODA_MAGIC 0xC0DAC0DA coda_file_info ``fs/coda/coda_fs_i.h``
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YAM_MAGIC 0xF10A7654 yam_port ``drivers/net/hamradio/yam.c``
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CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c``
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QUEUE_MAGIC_FREE 0xf7e1c9a3 queue_entry ``drivers/scsi/arm/queue.c``
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QUEUE_MAGIC_USED 0xf7e1cc33 queue_entry ``drivers/scsi/arm/queue.c``
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HTB_CMAGIC 0xFEFAFEF1 htb_class ``net/sched/sch_htb.c``
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NMI_MAGIC 0x48414d4d455201 nmi_s ``arch/mips/include/asm/sn/nmi.h``
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===================== ================ ======================== ==========================================
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2005-04-17 02:20:36 +04:00
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Note that there are also defined special per-driver magic numbers in sound
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memory management. See ``include/sound/sndmagic.h`` for complete list of them. Many
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OSS sound drivers have their magic numbers constructed from the soundcard PCI
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ID - these are not listed here as well.
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HFS is another larger user of magic numbers - you can find them in
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``fs/hfs/hfs.h``.
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