Re: DEVFSv50 and /dev/fb? (or /dev/fb/? ???)
Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Sun, 9 Aug 1998 10:00:49 +1000
Nathan Hand writes:
>
> On Sat, 8 Aug 1998, Richard Gooch wrote:
>
> > kragen@pobox.com writes:
> > > I must have missed the explanation of how autoloading of device-driver
> > > modules works with devfs. If a device is to be automatically loaded
> > > and configured when someone tries to access it, and devfs creates names
> > > in /dev as devices are loaded and configured, then how do you try to
> > > access the unloaded, unconfigured device?
> >
> > When you attempt to access a device node which isn't there (say
> > "ide/cd/c0b0t0u0") then for each path component that doesn't exist,
> > devfs sends that to kmod. Thus, potentially, you have have the
> > following sequence of strings sent to kmod: "ide", "ide/cd",
> > "ide/cd/c0b0t0u0".
> > In practice, people will have IDE configured into their kernel, so the
> > "ide" component is already there. Then the "ide/cd" string will be
> > sent to kmod. Now, if you have
> >
> > # /etc/modules.conf
> > alias ide/cd ide-cd
> >
> > then the ide-cd module will be loaded as required. Then the module
> > will detect your CD-ROM and will also register the "c0b0t0u0"
> > entry. So in general only one request is made to kmod: "ide/cd".
> >
> > Something to keep in mind here is that while device entries don't
> > appear/exist at first, an explicit lookup of the inode (any syscall
> > that provides a pathname) will trigger kmod. So it all just magically
> > works.
>
> Does this idea extend to auto-mounting?
>
> I know you can add post-install entries for kmod to follow, but will
> there be something similar to post-install entries for devfs?
>
> This would also allow devfs to make the nasty PCMCIA hack completely
> redundant, because adding devices could execute user space code.
If I understand what you mean, you are talking about telling a daemon
when new device entries are created. Then the daemon can do anything
you like (including mounting). Yes, read my message where I propose
such a mechanism.
Regards,
Richard....
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