[Dianne Hackborn]

Originally Posted by doctorow

I don't agree with the absolute seperation of kernel (Linux) vs. user land (Cobalt). The ones goes along with the other. Due to the new features introduced by having a Linux kernel (for instance the superb TCPIP stack), Cobalt would most likely also introduce new applications such as an SSH Client, etc.

This is actually a good example against what you are saying -- the Palm OS Cobalt APIs for dealing with networking are basically the traditional socket APIs, which would easily sit on top of Linux with no changes. Switching from one kernel to another would basically have no impact on applications using them.

There is nothing special about Linux that makes it magic to implement an SSH client. Cobalt has a good, modern IO system (using Streams), which can easily support such a thing. The main advantage you'd get in this area moving to Linux is that it would be a little easier to port some existing SSH client... except you still have to deal with UI code, which is really where most of the work is.

Originally Posted by doctorow

Also, hacker, you quoted FreeBSD. Remember that kernel and user land are very tightly integrated in this case. Unlike it is the case with Linux, everytime you update the kernel sources and recompile them, you should also do the same with the user land files.

I am not all that familiar with FreeBSD, but I find this statement surprising. When a new version of Mac OS X comes out (with a new version of its kernel), you don't have to recompile your existing applications, do you?

In fact, user space never directly calls into the kernel. Instead you supply shared libraries (libc being the prime example) that do the kernel calls for you, which give to user space an API that can be maintained across changes to the low-level kernel traps.

If your kernel and user land are "very tightly integrated" like this, I would say you've got a very basic flaw in your system design. It isn't a problem in Windows, Mac OS, the current Palm OS, etc., etc.

Originally Posted by doctorow

Hence I am *convinced* Cobalt, if it ever returns from vaporware, would look different if it was built on top of Linux.

I guess this bears repeating: "Palm OS for Linux" does not replace the current version of Cobalt. We expect devices to ship with Cobalt 6.1 this year.

As for things looking different, there is nothing about changing the kernel that says this. For example, you can run X Windows on Linux and FreeBSD, and switching between them doesn't change how it looks or operates. The "looK" is really one of the most trivial aspects in this.