Re: udev and devfs - The final word

Tommi Virtanen
2003-12-31T23:08:14Z

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?