Re: [Sheflug] Debian Box

[Al Hudson <nospam [at] york.ac.uk>]

On Wed, 10 May 2000, Richard wrote:

> >         It should be straightforward. First of all, forget about X, as
> > this can be sorted out later. So boot up, and log into a console. Move
> > the mouse around, and observe /proc/interrupts. Give the mouse a roll
> > over the table, and observer /proc/interrupts again. This looks like
> > this here (only relevant stuff considered)
> > 
> >            CPU0
> >  12:       5571          XT-PIC  PS/2 Mouse
> 
> no clue what this is about at all.  Certainly not on a Debian box.

:-) Quick reminder for newbies watching: /proc is a virtual filesystem,
that contains a lot of information about the system and it's state. By
virtual, I mean the files it contains don't actually exist on disk, it's a
representation of a filesystem.

/proc contains lots of stuff; /proc/pci for example contains information
on the pci bus. /proc/scsi contains information on the scsi adaptor, and
the devices hanging off it, etc. It's all useful stuff.

Why interrupts are useful here: every time a piece of hardware needs
'servicing', i.e, wants the CPU to take notice of it, it will (usually)
generate an 'interrupt'. In hardware terms, this means that the device
sends it's interrupt line (a pretty much direct wire straight to the CPU)
high, so that the CPU takes notice. In software terms, this triggers an
'interrupt handler' which takes care of the device: the device may be
signalling that it wants some information, or wants information to be read
from it, etc. Every time you move the mouse, it generates interrupts to
let the computer know that it's been moved. Thus, by watching
/proc/interrupts, you can see the computer is receiving interrupts from
the mouse, and the operating system has recognised this. Thus, it's a
configuration problem...

/proc is available on all distributions of linux, going back quite a few
versions now...

Cheers,

Alex.


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