Messages in this thread | | | Date | Mon, 04 May 2009 19:54:28 +0200 | From | Michael Riepe <> | Subject | Re: [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs |
| |
Hi!
Kay Sievers wrote:
> The problem is not the missing events, they could be pretty easily > recovered from sysfs with just another special hack to run at bootup - > it's the time it takes to bring up the engine to bootstrap /dev, to > allow us to start any other process which looks for devices. Today, > udev mounts /dev as a tmpfs, and at that point it is obviously empty, > and needs to be filled, and nothing else can reliably run at that > time.
And what about mounting /dev from an already populated image? Or, even faster, using the /dev directory of the root fs? That way, the device nodes would be present as soon as / is mounted, without any additional overhead, except the very first time the system boots (in case you choose not to populate /dev with a default set of device nodes in advance).
I know, not using tmpfs is a security risk and whatever. But does that really matter in an embedded system where you have no user accounts?
[...] > The plan is to start udevd, but run the coldplug in the background > and start other stuff in parallel, because you can be sure that all > currently known devices are already there, and the missing meaningful > symlinks created by udev will show up soon, along with a new event to > hook into. There will be no hard checkpoint anymore to wait for the > basic environment..
You can do that with a persistent /dev as well. It will even keep the symlinks udev created before the system rebooted. The only drawback is that you have to wait for device nodes that belong to new devices which were connected to the system while it was down. But that rarely happens, and will eventually be fixed by udev.
> The other important reason besides that it saves us from coming up > with just another custom hack to fill the initial /dev, is that it is > damn simple and very reliable.
Pardon me, but I have to ask this: Isn't your patch a custom hack, too?
-- Michael "Tired" Riepe <michael.riepe@googlemail.com> X-Tired: Each morning I get up I die a little
| |