Re: Who mounts sysfs?

[Greg KH <greg@kroah.com>]

On Thu, Jun 25, 2009 at 04:53:07PM +0100, Will Newton wrote:
> On Thu, Jun 25, 2009 at 4:18 PM, Greg KH<greg@kroah.com> wrote:
> > On Thu, Jun 25, 2009 at 11:36:29AM +0100, Will Newton wrote:
> >> Hi all,
> >>
> >> I'm trying to get the libertas driver working on an embedded
> >> development board and I've run into what looks like a sysfs problem.
> >> Although I'm actually using the BusyBox mdev hotplug helper rather
> >> than udev, I hope this is the right list to be asking this question.
> >
> > For busybox questions, not really, but we reserve the right to poke fun
> > at you for using mdev :)
> >
> >> What appears to be happening is I get my initramfs extracted, so I
> >> have access to the various necessary files including the hotplug
> >> helper and my firmware files. This step is taken care of by the rootfs
> >> initcall level. Then the driver initcalls are run, including the
> >> libertas setup routines, which call request_firmware. request_firmware
> >> fires off a uevent and calls the hotplug helper. The hotplug helper
> >> looks for the /sys/class/firmware entry for the libertas device, but
> >> it doesn't find one because I don't appear to have a mounted sysfs on
> >> the /sys mountpoint.
> >>
> >> So my question is: who should be mounting sysfs here? init will mount
> >> sysfs, but is run much later than the device initcalls.
> >
> > You need to mount sysfs as one of the first things to have happen.  Look
> > at your distro's startup scripts as an example of this.
> 
> Yes, I want my sysfs mounted as early as possible, but userspace (via
> /sbin/init) does not get a chance to do this until after the device
> initcalls have been run. I'm interested to know if there's a standard
> way to get sysfs mounted before /sbin/init is run.

There isn't.

> I could modify mdev to mount sysfs if it detects that it isn't
> already, but that seems like something of a hack.

Yeah, that sounds wrong.  Look at how your desktop distro does this,
this shouldn't be an issue.

thanks,

greg k-h