Modules and DevFS

From: William Knop (w_knop@hotmail.com)
Date: Wed Jan 31 2001 - 16:34:53 EST


I decided recently to go bleeding-edge on one of my Linux boxes and
discovered I had a problem with module loading while using DevFS.

Correct me if I'm wrong, but DevFS only makes /dev entries when a device is
present, and the device is not present until the module is loaded. So if I
want to access /dev/hda and the IDE module has not been loaded yet, I will
get a message telling me the device doesn't exist or some such instead of
autoloading the module and being happy. Same goes for hotswap devices,
right? I boot directly into X and have to crash out (otherwise it
continually tries to unsuccessfully load X) so I could enable my USB mouse
and various other devices.

I realize modularizing the entire IDE subsystem is not really good anyway,
because every time it reloads it will rescan the bus... But what about USB?
Suppose I don't have any IDE or USB devices, but want support so I can use
them later. Especially in the case of USB, plugability is a must for desktop
"home" systems.

I also have enabled the "module autoload" feature of DevFS, which
conveniently autoloads my 3c59x driver. :)

Does the kernel only autoload modules through userspace request, or can a
hardware request cause loading? For instance, inserting a USB peripheral
would cause the USB chipset to signal the OS. So therefore the OS can update
its device tables and unload the module again when it becomes inactive. This
goes for all hot-swap devices, IMHO.

I read all the FAQs and stuff and found nothing that really addresses this,
so here I ask if anyone has any idea as to a solution. No doubt I screwed
something up somewhere along the line... If my kernel or XF86 config files
are needed, I can pull 'em up and post 'em. Also, please CC responses to me
because I'm not currently subscribed.

Thanks a bunch,
Will

Box info:
  Linux 2.4.1
  Abit M/B
  P3 550
  256MB RAM
  AGP Devices:
    Nvidia TNT2 AGP display card
  PCI Devices:
    S3Virge/VX display card
    Adaptec 3940UW SCSI card
    3Com "Boomerang" ethernet card
  ISA Devices:
    SB AWE 64 Gold ISA sound card
  IDE Drives:
    2 CDROM drives
  SCSI Drives:
    4.5 GB UW drive
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