Re: udev and devfs - The final word

From: Tommi Virtanen
Date: Wed Dec 31 2003 - 18:09:05 EST


Rob Love wrote:
One thing that I'm confused about with respect to device files is how
kernel arguments are supposed to work. Now, we _seem_ to have a
mish-mash of different ways to tell the kernel which device to open as
a console, which device to use as a suspend device, etc.... Now, all
of the device names are being migrated to userland. How is the kernel
supposed to determine which device to use when it is told use
/dev/hda3 or /dev/ide/host0/something/part3 as the suspend partition?
The kernel no longer knows to which device this string this device is
connected.
...

The kernel uses the device number to understand what device user-space
is trying to access. The kernel associates the device with a device
number. Normally that number is static, and known a priori, so we just
create a huge /dev directory with all possible devices and their
assigned numbers (you can see these numbers with ls -la).

Let me try to rephrase Nathan's question more explicitly.

If user policy decides all naming, how does the kernel parse e.g. root=/dev/foo arguments? Or the swap partition to use for swsuspend?

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